197601 Byte Magazine Vol 00 05 Build a Light Pen

JANUARY 1976 $1.50 D the small sy Dy, Build a Light Pen What's Inside an LSI-II? Using Memory Address Space Golf Handicapping By Computer Introducin ...the world’s lowest cost computer system JO JOLT™ is the new, fully-tested microcomputer with the exclusive on-board DEMON™ debug monitor. You can build it, plug it in and talk to it in three hours orless . . . fora price of just $249! The basic JOLT™ card includes an 8-bit MOS Technology Model 6502 CPU, which requires no clock, can directly address 65k of memory, has two index registers, 58 instructions with 11 addressing modes, two interrupts and includes both single step and address halt capability. And that’s only a part of it. JOLT’s® CPU card is available IMMEDIATELY* in either kit form or as- sembled ($249 for the kit in single quantity and $348 assembled). Either way, the JOLT® CPU is completely tested prior to delivery. It comes complete with a termi- nal interface (TTY or EIA) and a unique software DEbugger/MONitor called DEMON®, for which full documentation is provided. It is very easy to program, and any JOLT® delivery includes an easy-to- follow assembly instruction manual, show- ing you exactly how to put everything together . . . correctly. Complete assem- bly should take you no more than three hours if you choose the CPU in kit form. Besides the JOLT® CPU — the 6502 from MOS Technology — the basic JOLT® card has a fully static memory accom- modating 512 bytes of the user RAM. The JOLT® CPU memory also has 64 bytes of interrupt vector RAM. ROM Program memory on the basic card consists of 1k bytes of monitor/debugger with an au- tomatic Power-On bootstrap program — so you can start talking to JOLT® and it to you as soon as you plug it in to your terminal. On-board Input/Output devices on the JOLT® CPU card include TTY 20 milliamp current loop and an EIA inter- face, both full duplex. The card has high speed reader interface lines and 16 fully programmable user |/O lines with full TTL drive. Nobody, but nobody, except MAI can offer you an on-board debugger/monitor like DEMON®. It’s fully documented, too. The exclusive DEMON® Debug Monitor really makes JOLT® one of the most out- standing computer systems offered at any time, at any price. Even without DEMON® and its superior software features, JOLT? is the lowest cost computer system in exis- tence. And DEMON® is a bonus you'll * have to use to believe. First, it self-adapts y All kits are delivered with a complete instruction manual and packaged for easy visual identifica- tion of parts to aid you in assembly. to any terminal speed from 10-30 CPS. With it, you can display and alter your CPU register and memory locations, plus you can read, write and punch Hex formatted data with Write/Punch BNPF format data for PROM programmers. !t has unli- mited breakpoint capability along with separate non-maskable interrupt entry and identification. External device inter- rupts can be directed to any location you choose, or they can be defaulted to DEMON® recognition. DEMON® also gives you (1) a completely protected ROM resident debug/monitor; (2) the capability to begin execution at any location in mem- ory; (3) the capability to bypass DEMON® entirely to permit full control by you over your system; (4) a high-speed 8-bit parallel input option; and (5) it includes user calla- ble DEMON® 1/O subroutines. MOST IM- PORTANT, DEMON® IS INCLUDED AS STANDARD WITH ANY JOLT® CPU KIT OR ASSEMBLED BOARD! Obviously, the JOLT® basic card is a computer in and of itself. But you can add significantly to its capacity and versatil- ity by adding 4k RAM JOLT™ memories — in one card or a whole bunch. A RAM card kit is only$265 ($320 assembled). Now. 4096 Bit RAM 4K BYTE The JOLT® memory card is a fully static 4,096-bit Random Access Memory (RAM) with 1 microsecond access time and on- board decoding. It is also available now.* And the quantity of one price is what you might expect to pay in quantities of 100 . . . very inexpensive! There’s also a JOLT® 1/0 card for you, our Peripheral Interface Adapter. You can’t beat the price — single kit 96 bucks — or the function. Pictured above is the assembled JOLT® CPU card with DEMON®. just plug it in and you're ready to go. The JOLT® PIA (Peripheral Interface Adapter) /O card includes two PIA LSI chips, 32 input/output lines, two interrupt lines, on-board decoding and standard TTL drive. It is also fully programmable and available IMMEDIATELY* in either kit or assembled form... at a very attractive single unit price ($140 assembled). Considering the function and capacity of the JOLT® Power Supply Card, you probably think the quantity of one price — $145 — is a misprint. It isn’t. The JOLT® family also includes a power supply card, which operates at any of three voltages — +5, +12 and -10. The power supply supports the basic JOLT CPU card, plus 4,096 bytes of RAM and \/O. The only two words for the price are “dirt cheap.” It is available for delivery immediately with a single unit kit price of $145 ($190 assembled) The assembled power supply card shown above powers the JOLT® CPU, 1/0, and RAM Memory cards. You can also choose a blank JOLT™ uni- versal card. Or several. The JOLT® Universal card is completely nude. It's a blank you can use any way you wish, for control panels, T.V. inter- faces, keyboards, LED's, or any other in- terface logic, because the card's holes are drilled to accept 14, 16, 24, or 40 pin sockets and has the same form factor as the other JOLT® cards. The single unit price is just $285. If you think you need extra cables, wires and the like, choose a Super Value JOLT Accessory Bag. A $55 Value for just $40. The JOLT®™ Accessory Bag includes 25 separate parts, enough hardware to con- nect one JOLT™ card to another. Order an Accessory Bag for each additional JOLT™ card. The Bag contains such necessary items as flat cable, connectors, cord spacers, hardware, wire, etc. weccccccccccccccsccoccecs ° ° THE JOLT PLAIN ENGLISH WARRANTY All components in the JOLT® family are new and fully tested prior to shipment. Kit components are fully warranted during the first 60 days of ownership. Assembled parts are fully warranted during the first 6 months of ownership. If your properly as- sembled kit does not work, just ship your order back to Microcomputer Associates Inc. and we'll repair, replace, or refund your money. coe Cececcccccccccccccccs eeccccccccccccccccccocs 20% BONUS NOW! Special ONE TIME BONUS DISCOUNT. Order one CPU before November 10, 1975 and deduct 20% off of all additional cards and ac- cessories. (Note: Discount does not apply to CPU cards, assembled or unassembled.) We told you JOLT™ was the world’s lowest priced computer system. These prices prove it. JOLT KITS {ALL PAYMENTS MUST BE IN U.S. DOLLARS) QUANTITY PRICING JOLT® ASSEMBLED PRICES (ALL PAYMENTS MUST BE IN U.S. DOLLARS) QUANTITY PRICING 14 5-19 20-49 50-99 100 up 1-4 5-19 20-49 50-99 100 up JOLT® CPU $249 $235 $230 $225 $215 JOLT® CPU $348 $325 $320 $315 $305 JOLT® RAM 265 255 250 245, 235 JOLT® RAM 320 305 300 295 280 JOLT? VO 96 90 88 82 E JOLT® 10 140 125 120 115 105 JOLT® POWER JOLT® POWER, SUPPLY 145 135 130 128 115 SUPPLY 190 175 170 165 150 ih JOT ERSAL ag) ag tSt__ THE NEW JOLT” FROM MAI IS AVAILABLE ONLY ON A DIRECT BASIS. JOLT® ACCESSORY USE THIS COUPON TODAY TO ORDER FROM may BAC 40 36 34 32 30 rTTIM ALL JOLT® KITS ARE DELIVERED COMPLETE WITH A DETAILED AND ILLUSTRATED ASSEMBLY MANUAL * Order will be shipped within 15 days. / Microcomputer Associates Inc. 111 Main St., Department G Los Altos, Calif, 94022 Phone (415) 941-1977 \ ©1975 Pehaco Corporation U ll ae ae This coupon will bring you a JOLT™! Complete and return it. Here is my check, money order or credit card payment for the following JOLT™ products. If a U.S. or Canadian order, please add $4.86 for shipping, handling and insurance. (Orders to all other countries are priced F.0.B. Los Altos and will be shipped FREIGHT COLLECT.) ‘Send me immediately: QUANTITY PRICE = PRODUCT. JOLT® CPU KIT JOLT RAM MEMORY KIT JOLT® 10 KIT JOLT® POWER SUPPLY KIT JOLT® UNIVERSAL CARD JOLT® ACCESSORY BAG JOLT® CPU ASSEMBLED JOLT® RAM MEMORY ASSEMBLED JOLT® 1/0 ASSEMBLED JOLT® POWER SUPPLY ASSEMBLED TOTAL $ +U.S./CANADA SHIPPING/HANDLING/INSURANCE NOTE: CALIFORNIA RESIDENTS, +6% SALES TAX TOTAL REMITTANCE (U.S. DOLLARS ONLY) s 4.86 Mail Pehaco Corporation, JOLT® Sales Agents YOUR Microcomputer Associates Inc. Dept. G ORDER 111 Main St., Los Altos, Ca 94022 TO: G All orders subject to the prior approval of the manufacturer. NOW! Special ONE TIME BONUS DISCOUNT. Order one CPU before November 10, 1975 and 20% deduct 20% off of all additional cards and ac- BONUS, cessories. (Note: Discount does not apply to CPU cards, assembled or unassembled.) PLEASE CHARGE THE TOTAL TO MY CREDIT CARD: BANKAMERICARD # MASTER CHARGE # 20% BONUS include digit #) My credit card expires on SIGNATURE All credit card orders must be signed) | UNDERSTAND THAT ALL U.S. ORDERS WILL BE SHIPPED VIA U.P.S. AND ALL INTERNATIONAL ORDERS WILL BE SHIPPED BY AIR. SEND MY ORDER TO: NAME ADDRESS ORGANIZATION ciry STATE zp PHONE ‘inelude Area Cade) *Make your check payable to: Microcomputer Associates Inc. International Orders: Payment should be cabled to Account #00417-06355 Bank of America, 215 So. Murphy Avenue, Sunnyvale, California, USA, 94086 hy seme sey amy a ser sys sm se se ol SOFTWARE — @ 8 8 @ BB Bis the best thing to feed your computer! Makes it healthy! Gets rid of that dull, aimless, blinking lights expression so many small systems exhibit these days. Feed your machine SOFTWARE! Make it feel good, Machine will then perform services. That will make YOU feel good. Put your machine on a good SOFTWARE diet like some of the following CHOW! ASSEMBLER PROGRAMS FOR THE ‘8008 Discusses a “minimum length’ Assembler program that can reside in 2K of memory, plus a more sophisticated version for those who have additional memory and desire a more powerful version. Included in this manual is a thorough explanation of the fundamental concepts of an assembler’s operation, details on how to format the “source listing,’ step-by-step analysis and presentation of subroutines, program flow charts, and assembled listings of the programs! Price? A very reasonable $17.95. AN 8008’ EDITOR PROGRAM Describes variations of an ‘’Editor’’ program that can reside in 2K of memory. Additional memory may be used to increase the size of the text buffer. The program enables one to manipulate “text'’ in order to create “source listings” or perform other kinds of text preparation. Includes discussion of routines, flow charts, and assembled listing. Priced at just $14.95. 8008’ MONITOR ROUTINES Describes a ‘‘Monitor Control’ package that allows you to control the operation of your computer from an external “keyboard” device. Various routines enable you to examine and modify memory locations and CPU registers, set “breakpoints” and execute programs for ‘debugging’ purposes, control bulk storage I/O devices, and perform other useful functions. This manual comes complete with subroutine explanations, flow charts, and an assembled, highly commented program listing. Low priced at just $11.95. NEW! — FOR HUNGRY 8080 MACHINES! AN 80 80’ ASSEMBLER PROGRAM This assembler program utilizes some of the unique routines we utilized in our popular ‘8008’ assembler which enables us to provide an ‘8080’ assembler that operates comfortably in 4K bytes of RAM (including the symbol table). An unusual feature of this assembler program is that it has been designed to accept mnemonics closely related to those used by SCELBI for our’8008' based machines. What this means is that programs originally written for an ‘8008’ unit can be directly processed by this assembler to produce object code for an ‘8080’ machine! NEAT! Of course, it also handles the extended instruction set of the ‘8080’ as well. This program is provided in our popular style of a manual that discusses the major routines, presents pertinent flow charts, and includes a highly commented assembled listing. $17.95. AN 8080’ EDITOR PROGRAM This is essentially a “carbon copy” of the material in our earlier manual describing a ‘8008’ Editor, except the assembled listing is provided with the machine code for an ‘8080.’ It is a good deal at $14.95. ‘8080’ MONITOR ROUTINES These routines perform the same types of functions as described above for the ‘8008’ version except routines were specifically developed to utilize the extended capabilities of the ‘8080’ instruction set. Great price at just $11.95. WANT TO “SPOON FEED” YOUR MACHINE? You CAN learn how to develop your own machine language programs. And, if you are really serious about utilizing a small system effectively, you had better plan on learning something about it sooner or later! Here is a good way to get started. MACHINE LANGUAGE PROGRAMMING FOR THE 8.00 & (AND SIMILAR MICROCOMPUTERS) THIS manual was written to provide the reader with the detailed knowledge one needs to know in order to successfully develop machine language programs. This information packed publication discusses and provides numerous examples of algorithms and routines that can be immediately applied to practical problems. Virtually all the techniques and routines illustrated in the manual can also be applied to other similar microcomputers such as 8080" systems (by applicable machine code conversion). The price of this exciting new manual is a low $19.95. (The floating-point arithmetic package presented in the publication is worth that price alone!) Prices given are for domestic delivery at book mailing rate. Add $2.50 for each publication if PRIORITY air service desired (U.S.) Overseas — include $6.00 for each publication for airmail service. (Pricing, specifications, availability subject to change without notice.) Order direct from: 1322 REAR BOSTON POST ROAD SCELBE COMPUTER & >: MILFORD CONNECTICUT 06460 CONSULTING INC In the Queue Foreground LET THERE BE LIGHT PENS ......... 00000 ece eee e + 26 Hardware — Loomis MPE line 4 seas aang PGCE TS ceeaee Applications — Helmers GOLF HANDICAPPING ..... Applications — Haller PHOTOGRAPHIC NOTES ON WIRE WRAPPING ........! 56 Techniques — Helmers Background Nucleus BYTE magazine is published monthly by Green Publishing, Inc., 70 Main St, Peter- borough, New Hampshire 03458. Subscription rates are $12 for one year worldwide. Two years, $22. Three years, $30. Second class postage application pending at Peter- borough, New Hampshire 03458 and at additional mail- ing offices. Phone 603-924-7217. Entire contents copyright 1975 by Green Pub- lishing, Inc, Peterborough NH 03458, Address editorial correspondence to Editor, BYTE, 70 Main St, Peter- borough NH 03458. NEW MINI-MICROCOMPUTER SYSTEM ........ Hee: 12 Processors — Baker HORROR STORY .......---- essere ee seeeanaemteere 31 Problems — Warren TOTAL KITCHEN INFORMATION SYSTEM .........++ AQ Systems — Lau INTEL 8080 OP CODE TABLE . Reference — Dittrich MORE TO BLINKING LIGHTS THAN MEETS THE EYE . .52 Applications — Helmers TAKING ADVANTAGE OF MEMORY ADDRESS SPACE . .60 System Design — Luscher Style — Peshka THE CT-1024 KIT .....-- 0. eee eee ee bees d eee eee weed 92 Review — Hogenson In This BYTE .. Beach Ball Software . BOMB ......... For the Joules, It’s a Steal Clubs, Newsletters MITS Computer Caravan ... That Didn't Take Long at All Classified Ads . . BYTE’s Bugs .. Answers to December Word Hunt . Sphere Rolls Into Town .. Letters bene Book Reviews eee The BYTE Questionnaire . Reader's Service . . New BYTE phone: 603-924-7217 BUTE #5 JANUARY 1976 nooo nt “Bi casts 1 In This BUTE On the cover, artist Robert Tinney has provided a scene depicting the combination of computers and golf handicapping described by Dr. George Haller in his article. How would you like a PDP-11/40 in your basement computer room? The price would probably be too high for the typical amateur. But Digital Equipment Corporation also makes the LSI-11, a microcomputer which implements the PDP-11/40 instruction set and inherits a wealth of existing PDP-11 software. Turn to Bob Baker’s article on the LSI-11 for a summary. How do you draw a picture on an oscilloscope display? Add a Light Pen as described by Sumner Loomis, and you will be able to add and delete points of light. When the LIFE program can’t figure out a key code, it calls DEFAULT, as described in LIFE Line 3. This issuc’s LIFE Line 4 specifies the DEFAULT routine used to enter cursor motion control data and numeric data for the KEY- BOARD_INTERPRETER. As a combined hardware and software system, the LIFE application enters the realm of hardware for the first time with a simple circuit to interface the cursor motion control keyboard and an ASCII keyboard via the same input port. Wire wrapping is a technique often used to assemble circuits. Turn to Photographic Notes on Wire Wrapping for some pointers for your own custom computer interfaces. According to tradition, no computer is ever complete without blinking lights. But There’s More to Blinking Lights Than Meets the Eye, or the control panel designer’s utilitarian motives. This issue provides a few ideas for using simple and inexpensive LED indicators in ways far removed from the traditional control panel application. 4 In the October BYTE, Richard Gardner commented on the application of personal computers in household situations. In this issue, Ted Lau continues on that theme with an article of “structured speculation” on the Total Kitchen Information System (TKIS). Computers solve problems, right? One problem which golfers have is calculating handicaps so that duffers can play against pros in the same tournament. In Golf Handicapping (or: Buy a New Peripheral with Money Earned from Your Local Duffers), Dr. George Haller describes a program he concocted to serve as the basis for a part time business calculating golf handicaps at his country club. For readers with teenage children, this might make a great opportunity for the kids to make some money to help pay for college expenses while learning how to run a business. Computer systems have many resources which can be used by the person who assembles or modifies the design. One resource which is very important is the memory address space inherent in the design of the computer. Taking Advantage of Memory Address Spaces by James Luscher can provide important improvements in speed and function of your system. What is style? In his article K or k?, Manfred Peshka describes some notational conventions which apply to BYTE’s unique combination of hardware and software information. While the change of these standards is incomplete in this issue, future BYTEs will employ the standard abbreviations and units throughout. What is one of the most useful peripherals? Why, the television set of course. To use the TV you need an interface. One such interface is the CT-1024 product by SWTPC reviewed by Jim Hogenson. Lowest Price in the World! In January of 1975, MITS stunned the computer world with the announcement of the Altair 8800 Computer that sells for $439 in kit form. Today MITS is announcing the Altair 680. The Altair 680, built around the revolutionary new 6800 microprocessor chip, is the lowest priced complete computer on the market. It is now being offered at the special, low price of $345! The Altair 680 comes with power supply, front panel control board, and CPU board inclosed in an 11" wide x 11” deep x4 11/16” case. In addition to the 6800 processor, the CPU board contains the following: 1. 1024 words of memory (RAM 2102 type 1024 x 1-bit chips). 2. Built-in Interface that can be configured for RS232 or 20 mA Teletype loop or 60 mA Teletype. 3. Provisions for 1024 words of ROM or PROM. The Altair 680 can be programmed from the front panel switches or it can be connected to a computer terminal (RS232) or a Teletype such as an ASR-33 or surplus five-level Baudott Teletype (under $100). The Altair 680 can be utilized for many home, commercial or industrial applications or it can be used as a development system for Altair 680 CPU boards. With a cycle time of 4 microseconds, 16-bit addressing, and the capability of directly addressing 65,000 words of memory and a virtually unlimited number of 1/O devices, the Altair 680is a very versatile computer! Altair 680 Software Software for the Altair 680 includes a monitor on PROM, assembler, debug, and editor. This software will be available to Altair 680 owners at a nominal cost. Future software development will be influenced by customer demand. MITS will sponsor lucrative software contests to encourage the rapid growth of the Altair 680 software library. Programs in this library will be made available to all Altair 680 owners at the cost of printing and mailing. Altair Users Group All Altair 680 purchasers will receive a free one year membership to the Altair Users Group. This group is the largest of its kind in the world and includes thousands of Altair 8800and 680 users. Members of the Altair Users Group are kept abreast of Altair developments through the monthly publication, Computer Notes. Altair 680 Documentation The Altair 680kit comes with complete documentation including assembly manual, assembly hints manual, operation manual, and theory manual. Assembled units come with operation and theory manuals. Turnkey model and CPU boards also include documentation. NOTE: A complete set of Altair 680 manuals in a 3-ring Altair binder is now available for $14.50 (regularly $25). Offer expires January 30, 1976. Delivery Personal checks take 2-3 weeks to process while money orders and credit card purchases can be processed in 1-3 days. Delivery should be 30-60 days but this can vary according to order backlog, All orders are handled ona first come, first served basis. Altair 680 Prices Altair 680 complete computer kit. Altair 680 assembled and tested : Altair 680T tumkey model (complete Altair 680 except front panel control board) Kit Only Altair 680 CPU board (including pc board, 6800 micro- processor chip, 1024 word memory, 3 way interface and all remaining components except power supply) . 195 Altair 680 CPU board assembled and tested............ $275 Option IC socket kit (contains 40 IC sockets. CPU, memory and PROM sockets come with 680 kit)....... $ 29 Option cooling fan (required when expanding 680 internally) Option cooling fan installed . PROM kit (256 x 8-bit ultraviolet, Connectors (Two sets of 25-pin connectors. Required when interfacing 680 to external devices)... Prices, delivery and specifications subject to change. MUTES “Creative Electronics” uerque, NM 87108 505/262-1951 CALL FOR PAPERS-ACM °76 OCTOBER 20-22,1976... HOUSTON Our 1976 Annual Conference will be held October 20 — 22 in Houston. We feel that it will be one of the most relevant ACM conferences ever held, both for the practicing professional and the researcher. The conference facilities in downtown Houston’s Regency Hyatt House will be outstanding. You will find that You are invited to submit a paper on any aspect of computer research, development, or implementation. High quality papers of a theoretical, state-of-the-art or tutorial nature are welcome. The technical program for ACM '76 will again be organized around the ACM Special Interest Groups, although additional sessions ACM ‘76 will be a place where you can enjoy your- self, renew old acquaintances, make some new ones, and participate in a serious technical discussion of the problems and potential of our industry. Plan to attend. will be provided for papers of general interest or those not related to any SIG. Papers must not have been previously presented or published; they should not exceed 10 published pages, including a 100-word abstract, bibliography, and illus- trations; and they must be received in four copies by March 1, 1976. All papers will be refereed either by the SIG’s or by reviewers selected by the Technical Pro- gram Committee. Notification of acceptance will be made by May 1. If you intend to submit a paper, and we sincerely hope that you do, please send in the coupon below. If you have an idea for a good session or some other technical program idea, please do the same or start promoting your idea in your SIG —— but do it now! Be a part of the spirit of ACM ‘76! Olin Johnson General Chairman, ACM ‘76 about the conference about the technical program Be a part of the “Spirit of ACM '76" / ASSOCIATION for COMPUTING MACHINERY 1976 ANNUAL CONFERENCE Roger W. Elliott Technical Program Chairman, ACM ‘76, Department of Industrial Engineering Texas A & M University College Station, Texas 77843 (713) 845-5531 Name Address city O11 intend to submit a technical paper. Tentative title State SIG (optional). (11 1 am enciosing a technical program suggestion. 1 Please call me. | would like to discuss an idea for the technical program. IMIEWIORIES ARE MADE OF THESE: s EROM BOARD inTEGRATED KEES AK BY 3 RAM CIRCUITS 8K By 8 BOARD. ..$352 (app $48 &We PROGRAM) BOARD $109.22 2102 1K Static RAM---sTILL onLy $1,95 4K By 8 BOARD...$200 (app $25 & We PROGRAM) ONE-THIRD OF A CENT PER BIT--- Our most popu- GUARANTEED FASTER THAN 750 ns, Buy 2K By 8 BOARD. $125 (a lar memory kit. You get sockets for all ICs, . ‘op $15 & WE PROGRAM) i fal = 100, take 20%; suy 1000, Taxe 30%, industrial-qual}ty plated-through board, lots Now you can stuff up to 8K of your favorite soft~ of bypars Ing. Paes, regulators to share the power load (less thermal problems, more 5203 2K EROM--- $9.50, THIS STATIC HHI]! ware----editor/assenbler or what have you----on |||[} reliability), typical 500 ns secess tine at MEMORY IS FULLY PROGRAMMABLE AND MAY MII|| board. Program it yourself or have us do the pro-||I[M} 25°C, and buffered addresses and outputs (no a -" i gramming, Just like the RAM kit, DIRECT ALTAIR Input presents more than 1 LPTTL load; out- ia Race with UV LiGHT, Non-VOLATILE 8800 PLUG-IN COMPATIBLE. Includes sockets, bypas- puts can drive 2 standard TTL loads). May 1---$24.50, sing, industrial - quality plated ~- through board, be powered with 8 volts unregulated; or bi ae ied 50, SIMILAR TO buffered addresses and outputs, on board regula- bypassing the on board regulators, with HE 2 BUT GK OF MEMORY. tion. LOW POWER: Full 8K requires $A @ 5V, 150 MEMORY/PROCESSOR 8 BIT CHIP SET: ma @ -12V. File protect feature includes tine re~ $32.50 BRINGS You 8 oF our 2102s AND AN 8008 MICROPROCESSOR. +5V. Complete with assembly instructions and logic print of the RAM board. ceiver with real hysteresis to prevent false trig- gering on noise. EXPANDABLE: If you buy our 2K board and want to move on to bigger and better things (like 8k}, all you add is more sockets and EROMS. Your board doesn't become obsolete. ALTAIR 9800 OWNERS, PLEASE NOTE: THIS MEMORY BOARD KIT, LIKE OUR OTHER MEMORY KITS, IS DIRECTLY PLUG-IN COMPATIBLE WITH THE 8800. ‘S We've got 4K by 8 boards pre-programmed with 8080 assembler, editor, and monitor rou- EROM BOARD tines. $200 buys you the same quality and ALTAIR PLUG-IN COMPATIBILITY as our other memory kits. Another advantage: because this is EROM rather than mask programming, you can make changes if desired. Speaking of changes, although these routines work SPECIAL OFFER our really well, we are including 2 free updates to purchasers should bugs or modifi- cations develop. Any additional changes are available for a very nominal charge. SEND $2.95 CPPD) FOR OUR SOFTWARE INFO PACKET IF YOU WANT MORE INFO OR WANT TO LOAD YOUR OWN ROM BOARD. INCLUDES INSTRUCTION LISTING, SCHEMATIC, ASSEMBLY DATA, ETC. TINY Rotary Switch SINGLE POLE, SEVEN POSITION + OFF. IN TO-5 CANy TINY FOR CIRCUIT BOARD MOUNTING. GooD -&eD$3608 : FOR PROGRAMMING & MUCH MORE. = 32 2102 (4k bytes RAM) faven congue rvoN BUT Yin Ne zs itecot ee ROM SON OF A MANY_AS THE LOGICAL SUCCESSOR AND OU! TO STANDARD TTL. —— DATA PACKET! CGHEAP TWLS90 Quad 2 input NAND gate .40 7MS04 Hex Inverter D5 apo WERFUL 16 BIT PROCESSOR. 40 PIN DIP; CAPABILITY FOR 45 TIPSOB Quad 2 Input AND gate «10 CLASSES OF INSTRUCTIONS AND UP TO 337 INSTRUCTIONS. INTERFACE eae ies jeue dP se cig CHIPS PROVIDE TTL COMPATIBILITY--RAMS AND ROMS PROVIDE MEMORY, TItSh2 BCD to dectnal deceue 125 AND THE PACE DATA PACKET TELLS YOU HOW TO APPLY EVERYTHING. 74LS138 VoF 8 decoder 1H pp CE DATA PACKET AVAILABLE SEPARATELY FOR $2.50 (COVERS PRINT~ Tatstes bie ye uerponm cnet 1-50 ING ANO POSTAGE). 80 PAGES OF INFORMATION ON THE CHIP ITSELF, FALS178 Quad latch 113g SOFTWARE, SYSTEM ORGANIZATION, AND MORE. ALSO INCLUDES AN 11! ed lace +38 By 17" INCH FOLDOUT LOGIC PRINT OF PACE IMPLEMENTATION, THIS IS THE SUCCESSOR TO OUR "CHEAP CLOCK’ KIT. IT IS AN EASY TO ASSEMBLE KIT THAT IN- CLUDES EVERYTHING YOU NEED TO MAKE A WORKING CLOCK, EXCEPT IF YOUR INTEREST IS MICROCOMPUTERS, AND PARTICULARLY PACE, You CASE AND HAROWARE. WILL WELCOME THIS DATA PACKET. PURCHASE PRICE REFUNDABLE WITH IT FEATURES 3/10 IN. READOUTS Hard to rogsrone wire ane -= SOCKETS FOR IC AND READOUTS fiued TH THe, Reno THE READOUTS CAN SE EASILY ‘BAL GODROUT ELECTRONICS REMOTED: THE CLOCK, IN CON- 35. OAKLAND AIRPORT, CA 94614 JUNCTION WITH OUR 60 HZ TIME 74273 8 bit latch (20 pin) 1.89 BASE ($10.95) IS AN EXCELLENT 1368 Noninv 3 st buf NOR en eH TERS: Add postage where indicated; add 50¢ to orders under $10. No COD AUTOMOBILE CLOCK. # Inv 3 state buf NOR en «| ondens; it's a Lot of paperwork for us. Californians add tax. To place ADD SHIPPING FOR 1 POUND. 74367 Noninv 4-2 buf w/ sep en 63 Bankamerécard® on Mastercharge® orders, cal (415) 357-7007, 24 hours a 74368 Inv4-2buf w/ sep en 63 day. Please eenenibet car 4 an answering service, and is not set up to BOTTOM~OF-THE-PAGE- ITEMS: 74390 16 pin dual decade cnt 1.50 handée technical ques: Lu340T: 1A regulator, T0-220 plas- 74383 14 pin dual binary entr 1.50 Want to know about a£e tthe “other stugg we se£e? Send for our FREE FLYER! tic package. 6 or 8 volts: 95¢ ea. TITLE: Microcomputer Dictionary & Guide AUTHOR: Charles J. Sipp! This new microcomputer dictionary fills the urgent need for all computer people, engineers, scientists, industrialists, communications people — as professionals, amateurs, teachers, or students— to become quickly acquainted with the terminology and nomenclature of a new revolution in computer control capa- bilities in areas that pervade most of man’s daily activities. Over 3500 definitions and explanations of terms and concepts (approx. 350 pages) relating to microprocessors, microcomputers and microcontrollers. There are also separate appendices on: programmable calculators; math and statistics definitions; flowchart symbols and techniques; binary number systems and switching theory; symbol charts and tables; summaries of BASIC FORTRAN and APL. In addition there is a comprehensive electronics/computer abbrevia- tions and acronyms section. Price: $14.95, MATRIX PUBLISHERS, INC. Dept. BM, 207 Kenyon Road, Champaign, IL 61820 Please send me the new MICROCOMPUTER DICTIONARY under your I 15 day no risk trial guarantee. If payment accompanies order we pay all shipping and handling charges. (Ill. customers add 5% sales tax) 1 —————— | Name I Address ] City State l Zip J Beach Ball Software What a predicament. You've bought this box full of printed circuit boards, trans- former iron and integrated circuit silicon. After long hours paying attention to the details of an intricate assembly process it is “done.” To the best of your abilities you’ve verified that the box does what it is supposed to do. Now it’s sitting over there ‘on the bench (or living room table (or office desk)) plugged into the AC wall outlet and grinning like a Cheshire cat with a mouth full of LED or TVT teeth. So, now what do you do with it? Like many objects of some bulk and substance, it seems so useless — but is it? There are lots of human designed objects which at first sight appear to be useless. But most turn out to have great potential value which can be released by the active and creative human mind. The secret of use and enjoyment is the application of that most characteristically human capacity to think. The hobby created about these artificial “brains” is an excellent training ground for the human brain — one of the secrets of its appeal. But Then, What Good is a Beach Ball Either? As an example of a simple object which requires creativity to realize its potential, consider a child’s beach ball. Imagine for a moment that your newly constructed com- puter kit is sitting on its pedestal and begins slowly to change into a beach ball through some advanced technological ‘‘magic.” Its corners begin to round, the edges smooth out, and after some moments of transforma- tion it is a jolly round beach ball having the same general properties the computer had: it sits there looking useless to the skeptic. As an intelligent and active being, curiosity is one of your most admirable traits. So you walk over to the pedestal, pick up that beach ball and begin a thorough examination of its characteristics. What do you find? As you pick it up you verify that it is a solid object which has the expected weight of a beach ball. You rotate it about several axes and verify that it is indeed a Editorial by Carl Helmers sphere within the limits of your perception. Using an appropriate measuring tool you find that its diameter is 30 cm. The surface is resilient but hard. The ball slips out of your hands and drops to the floor where its resilience is confirmed by a healthy rebound. After the examination, you put it back on the pedestal. Again, the thought: what good is a beach ball? It sits there with no life of its own, not even condescending to wink an LED at you. How could anyone possibly shell out hard earned cash for such an object? Beach Ball Software But peopie do shell out lots of hard earned money for beach balls. And people such as you and | are not fools when we buy a quality beach ball. We know beach balls are useful through our appreciation of fun and advertising of the products. The beach ball is the basic “hardware” required to play numerous games; beach balls are even used on occasion for more practical tasks. The beach ball is a widely distributed standard product with a simple design. Very little user documentation is supplied by the manufac- turers and distributors of beach balls. The wide acceptance of the beach ball is due to the numerous applications inherent in its design. These applications await the creative minds of human beings who decide what to do with the ball and how to do it. Any game or recreation which uses the beach ball as a prop is an example of the ‘“‘beach ball software.”’ Such games may have been made up generations ago and stored in the form of word of mouth learning, printed books or magazines on the subject. Or, they may be made up or reinvented spontaneously and never recorded at all. Whatever the source, the game and its rules form a method of using the beach ball which takes advantage of its properties, but is not in any way built into the device. So having temporarily approached the problem from the point of view of a beach ball, let's invert the transformation and turn the object back into a computer. We still BUTE staff PUBLISHERS Virginia Green, President Manfred Peshka, General Manager EDITOR Carl T. Helmers, Jr. PRODUCTION EDITORS Beth Alpaugh Judith Havey ASSOCIATES Hal Chamberlin Dan Fylstra Don Lancaster Chris Ryland PRODUCTION DEPARTMENT Lynn Panciera-Fraser, Manager Nancy Estle Neal Kandel Peri Mahoney Bob Sawyer PHOTOGRAPHY Ed Crabtree Bill Heydolph DRAFTING Bill Morello TYPESETTING Barbara Latti, Manager Marge McCarthy PRINTING Biff Mahoney INVENTORY CONTROL Marshall Raymond, Manager Kim Johansson CIRCULATION Judy Waterman, Manager Pat Geilenberg Dorothy Gibson Pearl Lahey Deborah Luhrs COMPTROLLER Knud E. M. Keller A manufacturer who supplies a series of interesting sample pro- grams to illustrate the use of his processor and system is providing you with a valuable service... have not solved the problem of where to get the specific creativity required for the com- puter software, but the beach ball analogy provides a useful model. A computer system, like a beach ball, is an incomplete system no matter how fully supported by manufacturers’ software. No manufacturer can tell you what you want to do with the machine in complete detail. The manufacturer can supply suggested uses and build in features which make certain uses inherently easy to program, but ultimately the user of the computer must decide what to program or when to use the programs available. The beach ball system is com- pleted when the beach ball user decides upon a particular game or practical applica- tion in which the beach ball is a key element. It might be that the beach ball simply makes the application easier to per- form, or it might be that the beach ball is so crucial that the application would not even have been possible without that ball. The computer system is also completed when you — the user — decide how you want to wD . a BOMB: svte's Ongoing Monitor Box BYTE would like to know how readers evaluate the efforts of the authors whose blood, sweat, twisted typewriter keys, smoking ICs and esoteric software abstractions are reflected in these pages. BYTE will pay a $50 bonus to the author who receives the most points in this survey each month, (Editor Helmers is not eligible for the bonus.) The following rules apply: . Articles you like most get 10 points, articles you like least get 0 (or negative) points —- with intermediate values according to your personal scale of preferences. Use the numbers 0 to 10 for your ratings, integers only. . Be honest, Can all the articles really be 0 or 10? Try to give a preference scale with different values for each author. . No ballot box stuffing: Only one entry per reader! Fill out your ratings, and return it as promptly as possible along with your reader service requests and survey answers. Do you like an author’s approach to writing in BYTE? Let him know by giving him acrack at the bonus through your vote. Page LIKED No. Article LEAST BEST 12 Mini-Microcomputer 012345678910 26 ight Pens 012345678910 31 Warren: Horror Story 0123456789 10 32 LIFE Line 4 012345678910 42 Lau: Kitchen Information System 0123456789 10 46 = Haller: Golf Handicapping 012345678910 50 Dittrich: Op Code Table 012345678910 52 Helmers: Blinking Lights 012345678910 56 Helmers: Wire Wrapping 012345678910 60 Luscher: Memory Address Space 012345678910 64 Peshka: K or k? 012345678910 92 Hogenson: CT-1024 Kit Review 012345678910 employ the computer. It might be that you use the computer simply to improve the efficiency of some menial task, or you might use the computer in an application — such as complex interactive games — which would have been impossible to perform minus the computer’s intelligence. Like any activity, you get out of a computer rewards which are in proportion to the effort applicd to under- stand and “get into” the activity. With computers — as with beach balls — it is often possible to find a starting point in this area of applications and software. Creativity of the individuals who have pre- viously thought about the subjects involved can often be useful as a starting point. By seeing concrete examples of the uses of the computer systems, you can acquire a valuable basic understanding of what can be done. One obvious source of such informa- tion is in the form of BYTE articles. Another form is in the user support packages provided by manufacturers. A man- ufacturer who supplies a series of interesting sample programs to illustrate use of his processor and system is providing you with a valuable service — you find out how things are done with his computer in specific and detailed examples. One excellent example of such a service is the documentation which can be purchased for the assembler and text editor programs of the SCELBI computers — complete listings of the programs with detailed explanations and design information are provided in the manuals for these SCELB! program products. When evaluating a computer system, look for such examples in the documentation and compare the offerings on this point. There are other sources of information about the creative uses of the computers of the world. Direct information can often be acquired in the context of the computer club, an association of users for the purpose of solving problems, exchanging ideas, filling in gaps in knowledge, etc. When you talk to your technological neighbor about what he or she is doing, you can get valuable information on the possible applications of your machine; and of course your neighbor receives similar benefits in return. It is this kind of exchange of creativity and ideas among interested individuals which will make the personal computing field into a well developed facet of our civilization, growing out of the scattered and isolated efforts of individuals who pioncered the activity. One of the main reasons for BYTE magazine’s very existence is to help foster this transfer of information, to give our readers the knowledge and ideas useful as creative starting points for personal applica- tions of computers, = Solder less. Design more. Whether you're a full-time engineer or spare-time hobbyist. there are only so many hours aday you can spend designing | and building circuits. So why not make the most of your time? Design circuits literally as fast as you can think. Instead of starting your next project with a soldering iron. save time by starting with our Design Mate™ 1. In acompact (7%4"W x 6%"D x 3%"H) case with a convenient sloping top. it offers solderless breadboarding at its best: 790 terminals; a continuously-adjust- able regulated 5-15 VDC 600 mA supply: and a DC voltmeter to monitor the internal supply or ‘The soldering iron. Asa design tool, it's obsolete. test your operating circuit. With Design Mate 1. hooking up (or changing) a circuit is as simple as pushing leads into holes on the breadboard. Rugged 5-point contacts insure reliable, low-resistance connections between resistors, capacitors. transistors...even IC's in TO-5 or DIP packages. And short lengths of solid #22 AWG wire make interconnections easy wherever you need them. At $49.95* complete, it’s not only a time-saver. it's amoney- saver, too. Larger capacity? Smaller capacity? Have it your way. Whatever your gy Py breadboarding needs, Proto-Board 103. 2250 solderless terminals save you time on every circuit you design. we can fill them. For larger capacity, save time with our Proto-Board* series—660 to 3060 terminal points, with or without built-in regulated power supplies. For smaller applica- tions, use 1 or more of our handy QT Sockets and Bus Strips, locking ? them together for T infinite expand- a ability, as you need ‘Test DIP swith i i eos “usm on the most crowdedcircuit’ save time and board with our Proto-Clip "series. money. Proto- Boards, QT Sockets and Bus Strips are just the beginning of the many ways we can help make your life more enjoyable: how about a foolproof, shortproof way to test DIP IC's—even in operating circuits—for just $4.50*? A full-featured, preci- sion function generator for $64.95*? A professional R/C bridge for $49.95*? A way to instantly see and monitor logic levels in an operating !C, without expensive scopes or elaborate procedures. And more, to save you time, money and aggravation. Time is money: Senerator only 364.9 Start saving it. Ask your CSC dealer Design Mi Design Mate 3: Precision R/C toshow you howto solder — ™ase-lust $49.95: less, design more and take the drudgery out of your electronic life. Or send for our free catalog and dealer list. “Manufacturer's recommended retail CONTINENTAL SPECIALTIES CORPORATION 44 Kendall Street, Box 1942 New Haven, CT 06509 ® 203-624-3103 TWX: 710-465-1227 West Coast office: Box 7809, San Francisco. CA 94119 © 415-421-8872 TWX: 910-372-7992 Canada: Len Finkler Ltd., Ontario © 1975 Continental Specialties Corp. 1 A New Mini - Microcomputer System The Digital Equipment Corporation LSI- II Robert W. Baker 34 White Pine Dr. Littleton MA 01460 Digital Equipment Corporation has a new addition to the microcomputer market. Designated the LSI-11, it is a complete 16 bit microcomputer system on a single 8.5 inch by 10 inch (21.6 cm by 25.4 cm) printed circuit board, combining the instruc- tion set of a PDP-11/40 with an under $1000 price. A 3.5 inch H by 19 inch W by 13.5 inch D (8.9 cm by 48.3 cm by 34.3 cm) boxed version of the LSI-11 is designed as an off-the-shelf microcomputer system. Desig- nated the PDP-11/03, it consists of an LSI-11 microcomputer, serial line interface, power supply, and a mounting box designed to mount in a standard 19 inch cabinet. Removing the front panel exposes the LS! modules and cables allowing replacement or installation of a module from the front of the PDP-11/03. The power supply has three front panel switches and _ indicators accessible through a cutout in the front panel. The lights and switches are still attached to the power supply and functional when the front panel is removed. Input power of the PDP-11/03 is typically 190 Watts at full load. LSI-11 Evolution The processor, memory, device interfaces, backplane and interconnecting hardware of the LSI-11 are all modular in design to allow custom tailoring necessary for specific appli- cation requirements. It was not intended to be a low end minicomputer, but to provide minicomputer capability to the new micro- computer applications. 12 To accomplish this goal, the LSI-11 was designed to optimize system costs rather than component costs. A four-chip micro- programmed central processor was selected to emulate the PDP-11 instruction set, allowing the inclusion of automatic dynamic memory refresh without additional cost. The microprogrammed processor also makes feasible user microcode and an ASCII con- sole which will be discussed later. Central Processor The central processor module consists of the microprogrammed processor and 4096 words of memory, together with the bus transceivers and control logic. The four chip microcomputer controls the time allocation of the LSI-11 bus for peripherals and per- forms all arithmetic and logic operations as well as instruction decoding. Eight 16 bit, general-pupose registers can be used as accumulators, address pointers, index registers, stack pointers, or other desired functions. Arithmetic operations can be from one register to another, from one memory location or device register to another, or between a memory location or a device register and a general register. Data transfers between IO devices and memory on the bus occur without disturbing the processor registers. Bus The bus, which is implemented on the H9270 card guide backplane assembly, is the data path which enables a complete system to be configured. This bus was designed to allow low cost peripheral interfaces for microcomputer applications, rather than to support the wide range of peripheral config- urations common to large minicomputer systems. The processor module is capable of driving six device slots along the bus without additional termination, as provided with the H9720 backplane. Devices or memory can be installed in any location along the bus, as most bus control and data signals are bidirec- tional, open-collector lines that are asserted when low. The bus signals include 16 multi- plexed data/address lines, 6 data transfer control lines, 6 system control lines, and 5 interrupt and direct memory access (DMA) control lines. Any communication between two devices on the bus is in the form of a master-slave relationship. Only one device, the bus master, can have control of the bus at any point in time. The master device controls the bus while communicating with another device on the bus, the slave. Since the LSI-11 bus is used by the processor and all 10 devices, there is a priority structure to determine which device gets control of the bus. Every device on the bus capable of becoming bus master has a specific priority associated with its position along the bus. When two devices request use of the bus simultaneously, the higher priority device will receive control. All data transfers on the bus are interlocked so that communication is independent of the physical length of the bus and the response time of the slave so long as a bus timeout does not occur. Asynchronous operation allows each device to operate at the maximum possible speed. Interrupt System Interrupt and DMA handling incorporates two daisy-chained grant signals. This method eliminates device polling to service interrupt requests and establishes an interrupt priority. The highest priority device is the module located electrically closest to the microcomputer module. Only when a device is not asserting a request does it pass grant signals to lower priority devices. When an interrupting device receives a grant, the device passes to the processor an interrupt vector which points to a new processor status word (PSW) and the starting address of an interrupt service routine for the device. The current value of the PSW and program counter (PC) are stored on the stack. The processor operates with the interrupt mask (PSW bit 7) set (1) or cleared (0). When PSW bit 7 is equal to 1, no external device can interrupt the processor with a request for service. The processor must be operating at PSW bit 7 equal to O for the device’s request to be effective. Interrupts can occur only between processor instruc- tions since they change the state of the processor. DMA operations, on the other hand, may occur between individual bus cycles since these operations do not change the processor state. One signal line on the bus functions as an external event interrupt line to the processor module. When connected to a 60 Hertz line frequency source, this signal line can be used as a real-time clock interrupt. When automatic interrupt dispatch (vec- toring) is not needed, this line may be used as a common interrupt signal. Although this necessitates device polling (as in earlier computers, such as the PDP-8), device inter- faces may now be slightly less complicated. A single connection on the processor module enables or inhibits the external event interrupt. When enabled, the device con- nected to this line has a higher interrupt priority than any device connected to the daisy-chained grant signals. Power Fail/Restart To further increase the system flexibility, several power fail/restart options are avail- 13 14 able. The power fail sequence is initiated upon sensing a warning signal from the power supply signaling an impending AC power loss. The current PSW and PC are pushed on the processor stack and a new PC and PSW are taken from a vector at location 24. Normally, with non-volatile memory, this routine would save processor registers, set up a restart routine, and halt. When only volatile memory is used, the registers cannot be saved but the power fail trap does allow an orderly system shutdown to occur. When AC power is restored, one of the four jumper selectable power-up options is initiated. The first option is loading a pro- grammed PSW and PC from the vector at location 24. This would be used with non- volatile memory to continue execution of the program at the point where the power fail occurred or to restart the program at an arbitrary address with ROM _ program storage. If the BHALT line on the bus (the halt switch) is asserted during this power-up sequence, the ASCII console microcode will be entered immediately after loading the PSW and PC. The second power-up option causes an unconditional entry to the ASCII console routines. The processor can then be started by an ASCII console command allowing remote system starting without controlling the bus halt line. (More on the ASCII console later.) Alternately, the last two options allow program execution to begin at a specified address in either macro- code or microcode. Memory The 4096 word memory on the basic CPU module consists of sixteen 4096 bit dynamic RAMs. This memory logically appears on the external bus while being physically on the CPU module. Being accessible to the bus allows external DMA transfers to take place to and from the basic 4096 word memory. Also, an optional jumper allows the CPU module memory to occupy either the first or second 4096 word block of the bus address space. Various memory modules are available for applications requiring more storage than the standard 4096 word MOS memory on the processor board. Those offered include a non-volatile 4096 word core memory, a 1024 word static RAM, read-only memory (PROM/ROM) with a maximum capacity of 4096 words per board in 512 word incre- ments or 2048 words in 256 word incre- ments, and a 4096 word dynamic MOS RAM. A common disadvantage of using dynamic MOS memory is the necessity of refreshing the contents of memory at specific intervals. The refresh operation is required to replace the stored charge in each The MODULAR MICROS from MARTIN RESEARCH Here's why the new M/KE 2 and MIKE 3 are the best values in microcomputers to- day! 8008 OR 8080 Martin Research has solved the problem bothering many potential micro users -... Whether to go with the economical 8008 microprocessor, or step up to the powerful 8080. Our carefully designed bus structure allows either processor to be used in the same system! The MIKE 3 comes with an 8080 CPU board, complete with crystal-controlied system timing. The M/KE 2 is based on the 8008. To upgrade from an 8008 to an 8080, the user unplugs the 8008 CPU board and plugs in the 8080 CPU. Then he unplugs the 8008 MONITOR PROM, and plugs in the 8080 MONITOR PROM, so that the system recognizes the 8080 instruction set. That’s about it! If the user has invested in slow memory chips, compatible with the 8008 but too slow for the 8080 running at full speed, he will have to make the 8080 wait for memory access—an optional feature on our boards. Better still, a 4K RAM board can be purchased from Martin Research with fast RAM chips, capable of 8080 speeds, at a cost no more that you might expect to pay for much slower devices. In short, the MIKE 2 user can feel confi- dent in developing his 8008 system with expanded memory and other features, knowing that his M/KE 2 can be up- graded to a MIKE 3—an 8080 system—in the future. EASE OF PROGRAMMING Instructions and data are entered simply by punching the 20-pad keyboard. Infor- mation, in convenient octal format, ap- pears automatically on the seven- segment display. This is a pleasant con- trast to the cumbersome microcom- puters which require the user to handle all information bit-by-bit, with a confus- ing array of twenty-odd toggle switches and over thirty red lights! A powerful MONITOR program is in- cluded with each microcomputer, stored permanently in PROM memory, The MONITOR continuously scans the key board, programming the computer as keys are depressed. Say the user wishes to enter the number 135 (octal for an 8008 OUTPUT 16 in- struction). He types 7, and the right- hand three digits read 007. Then he presses 3, and the digits say 073. Finally he punches the 5, and the display reads 135. Notice how the MONITOR program {Continued in column 3.) QUICK. what number is this? @Oo 080 808 If you have to read your microcomputer like this-bit by bit, from rows of lights--the computer's making you do its work. And if you have to use rows of toggle switches to program it, you might wonder why they call the computer a labor-saving device! Contrast the layout of a typical pocket calculator. A key for each number and function; six easy-to-read digits. Why not design microcomputers like that? Here they are! The modular micros from Martin Research. The keyboard programs the computer, and the bright, fully- decoded digits display data and memory addresses. A Monitor programina PROM makes program entry easy. And, even the smallest system comes with enough RAM memory to get started! Both the M/KE 2 system, with the popular 8008 processor, and the 8080-based MIKE 3 rely on the same universal bus structure. This means that accessories--like our 450 ns 4K RAM--are compatible with these and other 8-bit CPUs. And, systems start at under $300! For details, write for your... FREE CATALOG! MIKE 2 MANUAL... This looseleaf book includes full information on the MIKE 2 system, with schematics. Price for orders received by November 15, 1975... $19 Includes a certificate worth $10 towards a modular micro system, good 90 days. (Offer valid, USA only.) After 11/15: $25. [ modiar mics [marin rosea Martin Research / 3336 Commercial Ave. Northbrook, IL 60062 / (312) 498-5060 shifts each digit left automatically as a new digit is entered! The value on the display is also entered into an internal CPU register, ready for the next opera- tion. Simply by pressing the write key, for example, the user loads 735 into memory. The MONITOR program also allows the user to step through memory, one loca- tion at a time (starting anywhere), to check his programming. Plus, the Swap Register Option allows use of the inter- rupt capabilities of the microprocessor: the MONITOR saves internal register status upon receipt of an interrupt re- quest; when the interrupt routine ends, the main program continues right where it left off. We invite the reader to compare the pro- grammability of the M/KE family of microcomputers to others on the mar- ket. Notice that some are sold, as basic units, without any memory capacity at all, This means they simply cannot be programmed, until you purchase a mem- ory board as an “accessory.” Even then, adding RAM falls far short of @ conve- nient, permanent MONITOR program stored in PROM. Instead, you have to enter your frequently-used subroutines by hand, each and every time you turn the power on, EASY 1/0 INTERFACE The MIKE family bus structure has been designed to permit easy addition of in- put and output ports. A hardware inter- face to the system generally needs only two chips—one strobe decoder, and one latching device (for output ports) or three-state driving device (for inputs). A new 1/0 board can be plugged in any- where on the bus; in fact, all the boards in the micro could be swapped around in any position, without affecting opera- tion. 1/O addresses are easy to modify by reconnecting the leads to the strobe de- coder (full instructions are provided); this is in marked contrast to the clumsy input multiplexer approach sometimes used. POWER & HOUSING ‘The micros described to the left are com- plete except for a cabinet of your own design, and a power supply. The basic micros require +5 V, 1.4 A, and —9V, 100 MA. The 4K RAM board requires 5 V, 1A. A supply providing these volt- ages, and £12 V also, will be ready soon. OPTIONS ‘A number of useful micro accessories are scheduled for announcement. In addi- tion, the M/KE 3 and MIKE 2 may be purchased in configurations ranging from unpopulated cards to complete systems, For details, phone, write, or check the reader service card. 15 memory cell which has been lost through leakage currents. To eliminate most of the control circuitry normally necessary to per- form this memory refresh, the LSI-11 CPU microcode features automatic refresh con- trol. When enabled by an optional jumper, the CPU refresh control causes execution of a microcode subroutine approximately every 1.6 milliseconds; this operation refreshes all dynamic MOS memory in the system, not just the memory contained on the CPU module. While asserting a bus signal causing all dynamic memories to cycle at the same time, the CPU performs 64 memory references to refresh their contents. During the burst refresh time, external interrupts are locked out while DMA requests are still possible. Maximum memory size of the 16 bit LSI-11 is 65,536 bytes or 32,768 words. Usually the top 4096 words of memory on members of the PDP-11 family are reserved for peripheral device control and data buffers, so the nominal maximum main memory size is 28,672 sixteen bit words. However, the user is not required to dedicate the entire upper 4096 word space to IO, but may implement only what is needed. Octal addresses 000 to 376 are usually reserved for trap and device interrupt vector locations. Several of these are reserved in particular for software generated interrupts (TRAPS) as shown in Appendix A. Instruction Set All operations are accomplished with one set of instructions rather than the conven- tional collection of memory reference in- structions, operate/accumulator control instructions, and IO instructions. Single and double operand address instructions for words or bytes are used with a wide range of addressing modes, providing efficiency and flexibility in programming. The various addressing modes include sequential forward or reverse addressing, 8-bit byte addressing, 16-bit word addressing, and stack addressing. Using variable-length instruction formatting allows a minimum number of words to be used for each addressing mode. Each processor instruction requires one or more bus cycles. The first operation fetches an instruction from the location specified by the program counter (PC). If no further operands are required for executing the instruction, no further bus cycles are used. If memory or an 10 device is (RIGS ELECTRONIIcS| DISCOUNTS: 10% OFF ORDERS OVER $25.00; 20% OFF ORDERS OVER $250.00. SPECIAL +8008 ©69§50 8-2102 ANOTHER POWER SUPPLY... PS 25-1 0 to 25v 1a lab type power supply with adjustable current limiting; remote sensing & remote programming for voltage & current. Insturctions included. All parts except chassis, meter(s}, p.c. board. Kit of parts with schematics. $14.95 P.C. boards available, No. 007 $3.00 ea, 2K RAM BOARD KIT. ALL PARTS INCL. SOCKETS $84.50 ICs 8008 MICROCOMP. CHIP$30.95 2102 1K STATIC RAM _ 3.00 5203 256x8 PROM 15.00 5204 512x8 PROM 25.00 INFO ON ABOVE CHIPS IF ASKED FOR. ORDERS OF $50 OR MORE GET FREE BYTE SUBSCRIPTION IF ASKED FOR (CONTINENTAL U.S. ONLY). 008A MICROCOMPUTER KIT 8008 CPU, 1024 x 8 memory; memory is expand- able. Kit includes manual with schematic, program- ming instructions and suggestions; all [Cs and parts supplied except cabinet, fuses & hardware. Includes p. c. boards. $375.00 MANUAL ONLY, $25.00 (no discount on manual) 008A-K ASCII keyboard input kit. $135.00 QO8A-C Audio cassette adapter kit. $100.00 Details on computer, peripheral kits in our flyer. RGS ELECTRONICS 3650 Charles St., Suite K = Santa Clara, CA 95050 = (408) 247-0158 We sell many /Cs and components not listed in this ad. Send a stamp for our free flyer. TERMS OF SALE: All orders prepaid; we pay postage. $1.00 handling charge on orders under $10.00. California residents please include sales tax. Please include name, address and zip code on all orders and flyer requests. Prices subject to change without notice. 17 18 referenced, however, one or more additional bus cycles are required. A special maintenance instruction is included in the LSI-11 instruction set to aid in hardware checkout. This instruction stores the contents of five internal registers in a specified block in main memory. A diagnostic program may then be used to examine the information and determine the internal operation of the micro-level processor. The basic instruction set is that of the familiar DEC PDP-11/40 without memory mapping. Included are several operations normally not found even in other small PDP-11 processors, such as exclusive-or (XOR), sign extend (SXT), or subtract one and branch (SOB). There are also two new instructions used to explicitly access the processor status word (PSW). With the optional extended arithmetic chip, full integer multiply/divide and floating point arithmetic are also available. The instruction set is more comprehensive than that of the PDP-11/05 while the execution times are a little slower. Refer to Appendix B for a complete list of the LSI-11 instruction set and Appendix C for typical timings. The branch instructions make use of the condition codes (PSW bits 0 to 3) which are set after execution of every arithmetic or logical instruction. This allows more efficient use of memory by eliminating extra instructions and temporary storage locations typically used to check results of various operations. The result of every operation is directly accessible and can be modified under software control by using any of the Condition Code Operator instructions. A list of the four condition codes along with a brief definition of each is listed in Appendix Dd. Software Since the LSI-11 uses standard PDP-11 software, there is an extensive library of programs available from DEC _ including diagnostic programs to check out your system after it is built. There is also a DEC Users Society (DECUS) which makes avail- able a complete library of various PDP-11 programs at reasonable prices. Every LSI-11 owner automatically becomes a member of this organization. ASCII Console The conventional front panel lights and switches are replaced by an ASCII console/ ODT package that operates with any stan- dard terminal device communicating through a serial interface at a specific device address at any available baud rate. The functions available are very similar to those used by the familiar PDP-11 Octal Debugging Tech- nique and are shown in detail in Appendix E. These include examining and changing the contents of memory and registers, calcula- tion of effective addresses for relative and indirect addressing, and the functions of halt, single-step, continue and restart. By examining the contents of an internal CPU register, it is possible to determine which of the five methods of entering the console routines was used. Upon entering the console routine, the location of the next instruction to be exe- cuted will be printed followed by @. The console routine will then wait for one of the 14 legal command characters. Thus, the user retains all the direct hardware control of a conventional lights and switches front panel and gains the ability to boot load from a specified device in byte transfer mode. Interfaces The LSI-11 system includes several standard interface modules to handle a variety of applications. Currently both a serial and a parallel 1O interface is available, each as a single 8.5 inch by 5 inch (21.6 cm by 12.7 cm) PC board. The DLV-11 handles a single asynchronous serial line between 50 and 9600 baud, while the DRV-11 provides a full 16-bit parallel interface complete with two interrupt control units. The use of the two standard interface modules makes it very simple to connect any desired device to the LSI-11 bus. Standard devices such as teletypes, line printers, analog to digital converters, etc., can be connected directly to the interface modules with no additional circuitry. A simple cassette recorder inter- face can be made using the DRV-11 parallel interface, a UART chip, and a simple speed independent recorder interface circuit such as that shown in Don Lancaster's article Serial Interface, page 30, in the September issue of BYTE. @ Are you interested in buying one? This article has described the details of the LSI-11 computer by Digital Equipment Corporation. For those interested in pur- chasing the board version of this computer, the Southern California Computer Society is organizing a group purchase for amateurs, This purchase will involve an original equip- ment manufacturer (OEM) quantity of 50 or more machines, on a basis of cost plus 2% minimum contribution to SCCS. For further information contact Hal Lashlee of The Southern California Computer Society, at 213-682-3108. SCCS is organizing quantity purchases of other computer equipment, and is interested in making such offerings avail- able through other computer clubs. APPENDIX A: Location 999 OPA gp gl4 926 #24 939 934 960 ge4 199 244 APPENDIX B: LsI-11 MNEMONIC TRAP VECTORS Vector (Reserved) Time out & other errors Illegal & reserved instructions BPT instructions Ior instructions Power Fail EMT instructions TRAP instructions Console Input Device Console Output Device External event line interrupt FIS option INSTRUCTION SET INSTRUCTION Single Operand - General: CLR Clear word CLRB Clear byte COM (B) Complement (1's) INC (B) Increment DEC (B) Decrement NEG (B) Negate (2's complement) ‘TST (B) Test Rotate & Shift: ROR (B) Rotate right ROL (B) Rotate left ASR(B) Arithmetic shift right ASL(B) Arithmetic shift left SWAB Swap bytes Multiple Precision: ADC (B) Add carry SBC (B) Subtract carry SXT Sign extend Processor Status (PSW) Operators: MFPS MTPS Move byte from PswW Move byte to PSW Double Operand - General: MOV (B) Move CMP (B) Compare ADD Add SUB Subtract Logical: BIT(B) Bit test (logical AND) BIC(B) Bit clear BIS (B) Bit set (logical OR) XOR Exclusive OR BR BNE BEQ BPL BMI BC BvS BCC BCS Unconditional branch Branch if not equal to g Branch if equal to # Branch if plus Branch if minus Branch if overflow is clear Branch if overflow is set Branch if carry is clear Branch if carry is set Signed Conditional Branches: BGE BLT BCT BLE Branch if greater or equal to 9 Branch if less than % Branch if greater than § Branch if less or equal to 9 Unsigned Conditional Branches: BHI BLOS BRIS BLO Branch if higher Branch if lower or same Branch if higher or same Branch if lower Condition Code Operators: cLC cLV cLZ CLN cece SEC SEV SEZ SEN scc Jump & Subroutines: aMP JSR RTS MARK SOB Trap & Interrupts: EMT TRAP BPT I0T RTI RIT Clear C Condition Code Bit Clear v Clear Z Clear N Clear all condition code bits Set C Condition Code Bit Set V Set Z Set N Set all condition code bits Sump Jump to subroutine Return from subroutine Mark (aid in subroutine return) Subtract 1 & branch if not Emulator trap ‘Trap Breakpoint trap Input/Output trap Return from interrupt Return from interrupt Miscellaneous Instructions: HALT WAIT RESET NOP Optional EIS: MUL, DIV ASH ASHC Optional FIS: FADD FSUB FMUL FDIV Halt Wait for interrupt Reset external bus {no operation) Multiply Divide Shift arithmetically Arithmetic shift combined Floating add Floating subtract Floating multiply Floating divide Continued on page 22 19 NEW! ... WIDM-1 @ features- # ultra high speed intelligent display generates 16, 64 character lines of alpha-numeric data # displays upper and lower case characters # full128 ascii characters # single printed circuit card a Standard video output - $160-0°- SPECIAL FREE OFFER! Scientific Notation Software Package with Formatted Output The floating point math package features 12 decimal digits with exponents from +127 to —127; handles assigned and unassigned humbers. With it is a 5 function calculator package: +—X* & sq. root. It includes 3 storage and 3 operating memories and will handle chain and column calculations. With the purchase of (1) VDM-1 and (1) 4KRA-4 Memory: Just $299.00 (ofter expires 2-1-76) from- Processor Technology VIDEO DISPLAY MODULE ~ e 2465 Fourth S Corporation 9 220725; Continued from page 19 APPENDIX C: TYPICAL INSTRUCTION TIMING INSTRUCTION TIME (usec) ADD R1,R2 3.5 MOV R3,RO 3.5 MOV TAG1,19 (R2) 11.55 TSTB (R3)+ 5.25 BMI TAG2 3.5 SSR PC, 2(R2) 8.95 oMP (R4) 4.2 RTT 1g.5 Optional EIS & FIS Instructions: MUL 24 - 64 FADD 42.1 FMUL 52.2 - 93.7 FDIV 151 - 232 APPENDIX E: ASCII CONSOLE/ODT COMMANDS Command Function <cR> <LF> location. Up-arrow Open previous location. Back-arrow COMMENTS: Register addressing Relative & index addressing Auto-indexed Conditional branch Subroutine call Jump indirect Return from interrupt APPENDIX D: PSW CONDITION CODES Multiply Ploating add . CODE ——-PSW BIT Floating mult Floating divide N a z 2 v 1 c g Close opened location and accept next command. Close current location; open next sequential Take contents of opened location as a xelative address, and open that location. @ Take contents of opened location as absolute address and open that location. x/ Open word at location r. / Reopen the last location. $n/ or Rn/ Open general register n(f-7) or S (PSW). x;G or xG Go to location r and start program nL Execute bootstrap loader using n as device CSR. Console device is 177562. iP or P Proceed with program execution. RUBOUT <DEL> is a backslash (\). 22 Erases previous numeric character. Response CONDITION WHEN SET = 1 If result were negative If result were zero If operation resulted in an arithmetic overflow If operation resulted in a carry from the msb (most significant bit) or a 1 was shifted from the 1sb (least significant bit) Continued on page 24 Go Computer Now! Why not? FROM $860 TO $11,300 SPHERE CAN'T BE BEAT! SPHERE starts with a CPU using a Motorola 6800 microprocessor, a Real-Time Clock, 4K of dynamic memory, 1K of PROM software. The CRT Board generates 16 lines by 32 characters of ASCII on a television or video monitor. Keyboard is complete with numeric and cursor editing keypads. From here, hardware can be expanded to your hearts desire with extra memory boards (up to 64K), serial communications interface, cassette interface, Modem, digital I/O (as many as you need). Floppy Disk memory (up to 4 disks), 8 computer terminals, line printer etc...all from one M6800 chip. With a SPHERE Computer, stand-alone development is just the beginning, you can configure your system to handle your problem solving/record keeping needs. All SPHERE Computer Systems come complete with useable software languages. ‘Available are "PDS" 1K Basic, or extended Basic Compiler. When computer is turned on, it immediately goes into a comm- and mode, so that you can instantly start programming. PDS" contains a mini-assembler, editor, debugger, and utility comm- and set in 1K of PROM. Also available is a 1K subset of Basic. Our extended Basic compiler is complete with string, matrix, and file functions, and requires 12K of memory. With this software you can perform your applications whether it be account- ing, home management, education, security monitoring, research, business, etc. Why not invent your own application? For play or for work your biggest problem is no problem at all. $860 is the start for an operating Computer System Kit. Your computer is ready and comes complete with operator manuals sufficient for first-time computer users. Contact us today for more information. KIT ASM KIT ASM any ee ONE-CARD COMPUTER: Motorola 6800 microprocessor, 4KRAM, —_g999 gy49qr_ SPHERE2: Includes all features of SPHERE 1, plus serial communica- 512 bytes EPROM (containing a Program Development System), a tions and audio cassette or MODEM interlace. REAL-TIME CLOCK, 16 LINES OF DIGITAL VO, hard wired ROM Monitor, and a serial type interface. This is the 100-quantity price, 4459959 SPHERE 3: Includes all the features of SPHERE 2, plus memory extended to the hobby user for a limited time on a single unit. totaling 20k which is sufficient to run full extended BASIC Language. 522622 CPU BOARD: Motorola 6800 microprocessor, 4K RAM. IKEPROM — gigg 7995+ SPHERE 4: Includes all of the features of SPHERE 3, except the {containing an EDITOR, ASSEMBLER, DEBUGGER, COMMAND cassette has been replaced by an IBM-compatable Dual Floppy Disk LANGUAGE, CASSETTE LOADER, DUMPER, UTILITIES), and a REAL- System. This system includes a Disk-operating System and BASIC TIME CLOCK. Language and a 65 LPM line printer. 360 1400" SPHERE 1: Includes the CPU BOARD described above, plus 512 yarigys)_-« OTHER SPHERE PRODUCTS: Light pen option; {ull color and 8/)W character video with full ASCII keyboard and numericcursor video graphics system: low cost Dual Floppy Disk System; and full keypad, power supply, chassis, manuals and associated parts. {ine of low cost peripherals. “This ASSEMBLED SPHERE System includes the complete chassis, and video monitor as pictured below. ON WW SPHERE CORPORATION 791 South 500 West Dept. 129 (801) 292-8466 Bountiful, Utah 84010 23 24 Continued from page 22 BUS. BUS TIMEOUT DMA JUMPER SELECTABLE OPTIONS MACROCODE MICROCODE A collection of parallel data paths and power lines used to interconnect the various elements of the system, including the central processor, memory, and all peripherals. Bus timeouts or bus errors occur whenever the controlling device on the bus (the bus Master) does not receive a response from the addressed device (the Slave) within a certain length of time. In general, these are caused by attempts to reference non-existent memory or peripheral devices. Bus error traps cause processor traps through the trap vector address 4, Direct Memory Access. For high speed devices, memory may be accessed directly through the bus without the use of program controlled data transfers. The CPU module contains locations for six wire jumpers to contro! the various operating options as follows: 1, Two wires select which of the four possible power-up options is desired. These are normally set to restart through vector location 24 {so the LSI-11 acts as a standard PDP-11). 2. One wire jumper enables the external event (or real-time clock) interrupt feature when inserted. 3. One wire jumper enables the automatic dynamic memory refresh feature when inserted, 4, Two wire jumpers determine the addressing of the 4K RAM memory located physically on the CPU module. Each wire jumper consists of a short length of bare copper wire soldered between two designated holes in the PC board. The instruction set which the programmer sees and actually uses to implement his program, such as the PDP-11 instruction set in this case, The low level instruction set used in a microprogrammed processor to “emulate,” or execute, the macrocode. Microcode is more primitive in function, but executes at a higher speed than the macrocode. Pc POWER-UP SEQUENCE OPTION Oo 1 z 3 STACK TRAP VECTOR VOLATILE MEMORY Program Counter. A register which contains the address of the next instruction to be executed. Two wire jumpers on the CPU module select one of the four Possible power-up modes: POWER-UP PC at 24, PSW at 26, or HALT ODT — ASCII Console PC = 173000, or HALT Special processor microcode The power-up sequence is initiated upon supplying power to the processor module or on restoration of power after a temporary power fail has occurred. Processor Status Word, Contains information on the current status of the processor including the priority mask (bit 7) and the condition codes (bits 0 to 3). An area of memory set aside by the programmer for temporary storage or subroutine/interrupt sevice linkage. The stack uses the “Last In — First Out" concept; thus various items may be added to a stack in sequential order and retrieved or deleted from the stack in reverse order. Stack starts at the highest location reserved for it and expands linearly downward. In the LSI-11, register 6 is reserved as the hardware stack pointer and must be initialized by the software. However, registers 0 to 5 may be used for various program defined stacks as needed, Software generated interrupt. A unique address which points to a reserved set of locations (2 words) for interrupt or error handling. The first word contains the starting address of @ service routine (a new PC) while the second holds the new PSW to be used by the service routine. Volatile memory, such as RAM, will not retain useful information without power applied continuously. Non-volatile memory, such as core or ROM, will always retain its inform: with or without power applied, Memory Mania? 4K — $215! SK — $402! 122K — $562! I6K — $696! THE MORE THE MEMORY....THE MERRIER! The SPHERE Memory board. Is designed to hold 16K of memory on one board. 2107A-8 memory chips are used on this board and are designed in 4K increments to allow choice of 4, 8, 12, or 16K. Each memory chip is socketed and is delivered to you completely assembled and tested. The PC memory board connects to the CPU board tri-state buffered bus cables. The memory locations are strap selectable as to order of addressing. Those memory mania purchasers of 12 or 16K who have, or who buy, any SPHERE Computer System will get absolutely free the SPHERE extended BASIC com- piler. All documentations will be included. ITS ALL DYNAMIC MEMORY! I SPHERE CORPORATION Dept. 130 I 791 South 600 West I Bountiful, Utah 84010 Dear SPHERE: I] Yes! The facts I've read have convinced me! TG Piease rush me more details on your memory board. J] © Plesse rush me more details on your low-cost computer system and peripherals. (Specific questions, if any, are Bartaches.) [| Print name: Address: =PHERE CORPORATION 791 South 500 West Dept. 130 (801) 292-8466 Bountiful, Utah 84010 I City and State: Zip Code: Phone: a 26 RITTEN 0 NA et There Be Photo 1: The ease of removing just one dot from a full field display depends upon the display size. The author's X-Y display has an adjustable size control which was used in preparing this picture. Light Pens Sumner S. Loomis Loomis Laboratories Route 1 Box 131A Prairie Point MS 39353 soneeqepene Photo 2: The light pen can be used in an “erase” mode by filling the screen with “on” dots then selectively removing dots with the light pen. The titles added to this picture (and all the pictures in this article) were created with a separate character generator which is not described. 26 With only a few components and a few hours of construction you can add a versatile light pen to the oscilloscope graphics inter- face which has been described in the October 1975 issue of BYTE, page 70 ff. By holding the light pen to the face of the cathode ray tube (CRT), a point may be added or removed. This eliminates the awkward and time consuming effort required when using a program or manual switches to change the dots on the screen. The resolution and capability of the light pen are dependent on two characteristics of the CRT. The brightness and the size of the display tube will determine how easily you may add or remove one dot. An idea of the effect of display size may be had from photo 1, The word Test was written twice ona 12 inch (30.5 cm) black and white TV picture tube configured as an XY display like an oscilloscope. The top word was written with the display adjusted to an 8 inch (20.3 cm) size, and the lower word was written witha 4 inch (10.2 cm) display. Each letter was written with only one stroke of the light pen without touch up or corrections. With some practice, and possibly several passes, one dot may be added or removed if the display measures 8 inches (20.3 cm) or more. Further improvements to the pen are required with smaller display tubes. An advanced circuit that greatly improves the capability of the pen with small displays is also described in this article. The light pen can erase or draw depending on the setting of a switch. Examples of the two actions may be seen in photos 2 and 3. If the oscilloscope interface is adjusted for a high repetition rate, some smearing or carry over into the neighboring dot positions occurs. The author’s system has a front panel control permitting ten repetition rates. A small improvement in resolution can be noted at the lower writing rates, as shown in photo 2. A frame consists of 64 by 64 dots. Theory of Operation The light pen operates on the principle that brightness is quite intense during the actual interval that a particular dot is being written by the CRT’s electron beam. Although phosphor will continue to emit light for some time, the brightness decays in an exponential manner after the writing beam has moved on to the next dot. Figure 1 illustrates the simple light pen circuit. With proper adjustment of the sensi- tivity control (and possibly the brightness control), the photocell in the tip of the light pen will sense the moment in time when a dot is written at the particular location of the light pen. At this instant, the photocell will conduct, biasing the PNP transistor which causes a short pulse to be conducted through capacitor C1 to the base of the NPN transistor Q2. If the pulse is greater than .6 V, this transistor will be driven into satura- tion, and the light pen output will fall to .3 V. This output line is the connected to pin 5 of the oscilloscope graphics unit which writes a 1 or a O bit (dot or no dot) at precisely the instant that the dot position touched by the pen was addressed. The above procedure works quite well if the dot to be changed is illuminated at the time. With proper adjustment of the sensi- tivity control, we can usually use an illum- inated dot just above the point of action (it must precede the dot in scan sequence) to create a new dot in the next space. This action of extending a line can be quite useful for drawing bar graphs on the CRT. This mode of entry is possible because screen persistence allows the light pulse to be carried over into two or three subsequent dot positions depending on the frame speed. How can the photocell sense the dot’s position if there is not any illumination to trigger it? This is accomplished by the flood circuit which is shown in figure 2. This circuit overrides the normal Z-axis control and floods the screen with light by feeding a logical one signal to the Z axis of the display ‘unit. With this arrangement the pen is placed at the required dot position, the footswitch is actuated to flood the screen with light, and the photocell is energized when the Bat il Wat FREE-HAND WRITING Photo 3: The light pen can be used in an “enhance” mode by using a footswitch control to flood the screen momentarily when the light pen is in position. PC RI SENSITIVITY MFG __PHOTOCELL|CONTROL Tl H-35 IM 1 H-38 2M 1 L-63 5K CLAIRE 903 20K LIGHT-PEN OuTPUT LIGHT PEN PC-1 Figure 1: The simple version of the light pen can be constructed according to this schematic, All resistors 4 W. RI FROM DDU CARD coal To OSCILLOSCOPE Z OUTPUT Z INPUT R2 ths -av R3 6 or 390-22K T a Or FOOT SWITCH SI Figure 2: The foot switch control used to flood the screen for “enhance” mode operation is given in this circuit which modifies the Z-axis signal to the oscilloscope driver. 27 28 ca ca +5V Ole 20pF CHAR GEN 10 PINS WRITE S3 ea} one- [of SHOT R2 NOL sk r@ (00K rao mal @} Sher Noe — La MIN. PHONE 4528 CMOS és tI] © 33uFy iI oO iI! a i il il to I! rs O) i}! 1 of i} < bl J LIGHT PEN PC-I mn Figure 3: By adding a pair of oneshots to the circuit, the ability to draw pictures is improved through a short data lockout period which avoids smearing. writing beam reaches that particular dot position. Releasing the footswitch removes the flood and allows the data to be examined. The circuits just described will probably suffice if you wish to use the light pen only for occasional correction of data. If you plan extensive and detailed work, such as cartooning or statistical data entry, a modifi- cation of the circuit will allow you to tailor the light pen’s response to your own particu- lar needs and system speed. The circuit shown in figure 3 is similar to the one shown in figure 1. However, it includes two oneshot multivibrators (contained in one CMOS DIP). The first one produces a constant amplitude pulse of approximately 200 nsec duration which is sufficient to bring about the storage of a 1 or 0 bit in most versions of the 2102 memory (ICs 11 to 14 in the oscilloscope graphics interface). The second one delays the generation of another write command for .25 sec, giving the operator sufficient time to withdraw the pen from the screen or move to a new location, before a double or multiple dot can be drawn, Once the two pulses have been timed in accor- dance with a given system speed and the operator’s writing speed, it becomes very easy to draw detailed images with the light pen. In figure 3 resistor R4 and capacitor C1 control the length of the write pulse, and resistor RS and capacitor C2 control the wait time. For the 4528 CMOS oneshot, the time of the pulse (T) measured in micro- seconds is a function of resistance (R) and capacitance (C) measured in ohms and microfarads, respectively, as follows: T=2,5*R*C ** 85; where a single asterisk denotes multiplica- tion, and a double asterisk exponentiation. The circuit shown in figure 3 also includes a switch and connections for using the light pen with the author's text display and editing system, Exact details for this connection are not given here, as they will differ with the type and construction of the text display system. | found, however, that the shift register type memories commonly used in these systems require a much longer write pulse than is necessary for the 2102 memories. It was also desired to eliminate the holdoff circuit (second oneshot) for this application. These changes are accomplished with switch S1 and resistors R9 and RS. If these features are not desired, it is recom- mended that R9 be replaced by a wire, R4 changed to 4.7 kQ and C1 to 20 pF. Construction As is shown in the table accompanying figure 1, several different types of photocells are suitable for use in the light pen. The Texas Instrument (Tl) type H-35 or H-38 is avery small device with a built in lens. These were originally designed for use in punched tape and card readers, thus the small size. Their size, sensitivity, and restricted field of view make them ideal for this application. The high impedance of these devices, how- ever, makes them somewhat slow for this application, particularly at low brightness levels. The slow response time limits their use at the faster scan rates, and complicates the smearing mentioned earlier. Another device, the L-63 type which is available from Radio Shack (276-140 infared detector), was found to be considerably faster. Being a much larger device, however, it has a larger field of view, and much of its speed advan- tage is lost to optical smearing. Models of both photocell types were built and tested by me, with only slight preference for the H-35, With some careful masking, and possibly the addition of a small, short focal length lens (e.g., Edmund Scientific number 12050 cylinder lens, or a small drop of clear epoxy), this photocell will probably perform better than the H-35 for this application. The Claire types 903 and 903-L were tried with only fair results. Any ball-point pen or felt-tipped marker can be reworked to make a housing for your light pen. Take a tour of the local stationery store to find likely candidates. The L-63 photocell was found to fit nicely into the end of a Graphi-100 marker pen which can easily be disassembled with diagonal cutters. An example of the construction with the L-63 is shown in photo 4, and the H-35 assembly is shown in photo 5. Secure the photocell in place with epoxy adhesive after attaching the shielded cable. The cable can also be secured against damage from pulling by filling the entire pen with silicone rubber adhesive or ordinary house- hold bathtub caulk. It is wise to keep the cable short, especially with the H-35 or H-38 photocells, to obtain maximum possible response speed. | used an 18 inch (45.7 cm) long miniature coaxial cable leading to a miniature phone plug. If you are using the simple circuit of figure 1, the parts can be assembled on a small turret terminal board available at most electronic supply houses. This assembly is shown in photo 6. The circuit of figure 3 can be assembled in the same manner with the addition of a 16 pin DIP socket. R4, R5, C1 and C2 should be mounted in such a manner that they can be changed easily (Cambion 601-1512 component clips are useful here). <a \S Photo 4: This shows a pen based on the TI type L-63 photocell, built using a marking pen case, Photo 5: This picture shows an assembled light pen using a TI type H-35 (or H-38) photocell with a standard ballpoint pen housing. Ess Photo 6: This photo illustrates how the circuit of figure 1 can be assembled using a small turret terminal board. The transistors and R5 are mounted out of sight on the rear side of the board, 29 IMPROVED FREE-HAND WRITING Photo 7: Using the improved circuit of figure 3 reduces much of the over-writing of multiple dots which occurred using the original circuit of figure 1, This is an enhance mode picture, Photo 8: This illustrates a cartoon drawn using the erase mode of operation with the improved circuit of figure 3. 30 The sensitivity control may be conveniently mounted on the front panel. The operation of the light pen requires control of the inputs to the oscilloscope graphics unit. | have found that one of the most convenient ways in my system is through a set of manual data switches. This type of input was illustrated as a test fixture for the oscilloscope graphics interface in figure 5 on page 75 of the October 1975 issue of BYTE. In my system, these data input switches are shared with a Mark-8 minicomputer front panel by means of an 8 pole double throw toggle switch. It is also possible to set up input codes to the oscilloscope graphics unit using software in the microcomputer system which drives it. In order to enter data with the light pen, a deposit switch is pressed whenever the pen is in the proper position for data entry. The deposit switch should be mounted in a convenient location near the display tube and light pen. In my system the light pen deposit switch was mounted next to the original deposit switch of the Mark-8 com- puter. Using The Light Pen To illustrate the use of the light pen, we will cover the procedure necessary to draw a simple figure on the screen in the erase mode using manual controls. Set the switch register to 1000 0110 binary (turn scan on) and depress the deposit switch. This should produce random dots on the screen. Set the switch register for 1000 0010 binary (set Z on) and depress the deposit switch again. The screen will show a full field of dots. (If the Z axis polarity of your display tube is reversed, you will have to use the “‘set Z off” command (1000 0011 binary) to illuminate the screen.) Set the switch register for 1000 0010 (set Z on), but do not activate the deposit switch. Now bring the light pen in contact with the display CRT, and note that the dot or dots within its field of view are erased. To erase the entire screen and start over, simply press the deposit switch and repeat the above procedure. To write in the enhance mode (screen dark, writing illuminated dots), reverse the above procedure by wiping the screen clean with the “set Z off” command (while the scan is on), and after setting the switch register to “set Z on” without the deposit switch, proceed to write dots with the light pen. In this mode, the flood foot switch must be periodically activated to provide the required illumination. Examples of the light pen’s drawing capability can be seen in photos 7 and 8. # Horror Story Not too long ago, researchers at Stanford Medical Center in California were horrified to discover that several years of data that were stored on magnetic tape had disappeared. The tapes hadn’t disappeared, just the data. The discovery was made when they attempted to retrieve some of the data for analysis, but found only “garbage” recorded on the tapes. Even more disturbing was the fact that these tapes were supposed to be ultra reliable. They had been especially developed for storage of important research data and used a fully redundant recording technique for improved reliability. Fully redundant recording is a storage technique in which each data bit is recorded in two different locations. In this case, DECtape™M was being used. This is tape that is 3/4ths of an inch wide and has six parallel data recording channels or paths. The data recorded in the three channels on one side of the tape is duplicated in the three channels on the other side. Thus, the tapes have half the data capacity that they could have, but their reliability is signifi- cantly improved. It should be noted that there are a number of other possible redundant storage techniques in use for improving reliability. For instance, ‘‘triply redundant recording” replicates each bit three times in three separate locations. Alternatively, depending on the allowable bit-patterns that may be used to store data, ‘partial redundancy” may be used. In this technique, a computation is performed on the explicit bit-pattern of each datum. The computation result requires fewer bits than the original datum, but may be used to either replicate the original datum (thereby recovering it, if necessary) or to at least verify the authenticity of the original datum. These are referred to as “error-correcting codes” and “‘error-checking codes,” and form an on-going area of applied-mathematics research. In either case, partial redundancy is important in that it improves reliability, but requires less additional storage than full- or triple-redundancy. First, the researchers thought (prayed) that their tape decks were malfunctioning. Not so. Diagnostic checks were made and the tape equipment was working properly. Next, the tapes were examined. Nothing was wrong with them, physically, and in fact, new data could be recorded on them and retrieved without difficulty. They asked others around the Medical Center if they had encountered similar problems (there are about 50 computers at the Stanford Medical Center). None had. Then they looked for environmental causes, but there appeared to be none. The temperature and humidity recorders, common to biomedical research fac es, indicated no significant fluctuations. There had been no fires, no chemical accidents, and there was no x-ray or high power electronics gear in use nearby, The tapes had been in their individual boxes, just like the tapes for all of the other computer facilities in the Medical Center, and these boxes had been neatly stored on the bottom shelves of a cabinet, well out of the way of possible harm. It was a most frustrating puzzle. Finally, however, the mystery was solved. It seems that the janitor had made his biannual floor polishing rounds, using a heavy duty rotary floor polisher. The magnetic radiation from its massive motor, in proximity to the low shelved tapes, had raised havoc with the bit patterns that had been recorded on the tapes. The researchers now store their tapes on the top shelves, = Jim C. Warren Jr. Star Route Box 121 Redwood City CA 94062 31 LIFE Line 4 Integrating graphics control commands Car! Helmers 32 In LIFE Line 3, the design of the DECODE routine of the LIFE program was presented. DECODE is designed as a table driven mechanism for selecting one of several subroutines which carry out the functions of the LIFE program’s KEY- BOARD_INTERPRETER. However if you examine table 1 of LIFE Line 3 (see p. 51 of BYTE #4), you will note one conspicuous and intentional lack: There are no routines which process the interactive graphics com- mands required to set up LIFE patterns on the scope display. Yet in LIFE Line 1, several special purpose keys were introduced as manual inputs for cursor motion control and data definition purposes. Where is the missing part of the program which interfaces these keys? What are the hardware implica- tions of requiring a special keyboard? Answers to these questions are the major concern of LIFE Line 4. Integrating the graphics control commands is a combined hardware and software topic. The software is that of the DEFAULT routine that inter- prets several keyboard inputs not handled by DECODE; the hardware consists of the design of a special keyboard interface to automatically switch between an ASCII key- board’s 7-bit parallel output code and the LIFE graphics con