87.06 apple bug

APPLE—BUG is the Newsletter of APPLE-Q: the Brisbane Users’ Group. Post Office Box 721 - South Brisbane - Qld 4101. DHE I CK 2c 2c ic 2 ic 2K ic 2c ic 2k kK i 2K i ok June 1987 DAK IK 2K Re 2c ic ic ck ic 2 ic i KK 2k 2 2 2 ok Ok [ In this issue ] > Special Attraction <¢ > Registrar’s Notes < > Editor’s Notes < > Treasurer’s Notes < > BBS Report < > Secretary’s Notes < > Software Library < > Feature Article < > Advertisement ¢ > Special Discount Offers < > Membership Renewal Form <¢ NEXT MEETING:— 21st JUNE 1987 (We got the date right this time) <<¢ CREDITS >>> Graham Black -> He typed it all in Tony Truscott -> He added the mistakes ZARDAX II -> Word Processing EPSON LQ-1500 -> Typesetting The Hooper Centre -> Printing & Distribution The APPLE Computer -> The reason for it all Registered by Australia Post - Publication No. QBG 3485. APPLE- BUG <2> June L9K7 [ Executive Committce ] Terry Sweetser - President Ph. (07) 203-4210 Bernie Benson Vice-President Ph. (07) 345 1545 Vince Crosdale - Secretary Ph. (07) 351--3090 Eric Conolly Treasurer Ph. (07) 261 1860 Graham Black - Registrar Ph. (07) 883 1525 Tony Truscott Editor Ph. (07) 266 4795 Peter Lane-Collett - Assistant Editor Ph. (07) 398-9282 Richard Egglesfield Hardcopy Librarian Ph. (07) 349 8888 Bob Godbehere - Software Librarian Ph.(07) 808-3892 [ Bulletin Board System (BBS) i] Apple-Q BBS : online 24 hrs Telephone : (07) 284-6145 (DATA) : (07) 883-1525 (VOICE) Baud Rates : 300, 1200/75, 1200 and 2400 (CCITT and BEL) Data Specs : 7 Data bits - 1 Stop bit - No Parity (Full Duplex) Sysops : Grahas Black - ph. 883 1525 : Vince Crosdale — ph.351--3090 BBS equipment : Apple //e 128k : 1 x 800k 3.5" drive : 2.x« 1 meg. Ram Cards Calls to the system : 4146 Registered Users : 277 (as of midnight 7th June) SYSOP stands for: SYStem OPerator BRS stands for: Bulletin Board Systcm The BBS will be on show at each Open Day. { What.’s When ] Sunday 2lst June 1987 Open Day at the Hooper Centre. Hours: 9.00.am. till 4.30.pm. Monday 22nd June 1987 Committee Meeting at the Hooper Centre. Starts: 6.30.pm. Sunday 19th July 1987 Open Day at the Hooper Centre. Hours: 9.00.am. till 4.30.pm. Monday 20th July 1987 Committee Meeting at the Hooper Centre. Starts: 6.30.pm. APPLE-BUG <3> June 1987 {[ Special Attraction ] * eK * &*«& MAC TI DEMONSTRATION * * * XX Peter Newland from Computer City will be bringing the MAC II along with the MAC SE and the //GS, to this months meeting. Peter will also be displaying some software for the //GS. {C Registrar’s Notes ] Mailing labels. Please take note......... Your membership number and membership expiry date are on the first line (at the top) of the mailing label. This is the only notice you will receive that your membership is due to expire. If your membership is in arrears by more than six (6) months, you will be required to pay the joining fee of $10. If you do not receive a newsletter, then either your membership will have expired, or you have changed your address without telling us. Example: MBR # 0999 - Exp: JUNE 87 BLOGGS . JOE 34 BLOGGS CRESENT BLOGGSVILLE.QLD 49993 Many thanks to the few members who have taken the time to fill in the Membership Renewal forms, and return them to us so we could update the club records. At the March Executive Committee meeting, the matter of increasing the membership fees was discussed at length, and increased. Joining Fee: $10 Adults/Family: $20 Students/Pensioners: $12 Corporate Membership: $50 Associate Membership: $10 till MAY 88 (BBS users only) (Students under 21 years - Pensioners on production of Pensioner Card) ( at the discretion of the Executive Committee) 0000000000000 The coffee machine at the Hooper Centre does not belong to the club. We have been given permission to use it, but the coffee costs 20 cents per cup, with or without the contents. The cups are not to be used as buckets in the sand pit, and they are not there to be used as ashtrays. If you require a cup for some reason other than coffee, then please get one from the bin. The 20 cents for the coffee should be left on top of the coffee machine in the container provided. APPLE BUG June 1987 L Editor’s Notes ] by Tony Truscott Hello, this is the first newsletter that I have edited and so in this issue I have been mainly learning the procedures used in getting the newsletter to press. When I learn more about the setup I hope to instill some new ideas into the newsletter and I would like to hear your views. If there is something you would like to see in the newsletter then 1 want to know about it. You can either leave a message on the BBS or leave a note for me at the Open Day. I have been told that I must write enough in my notes to fill up a page! So let me give you with some background information about myself (they’1] never force me to write too much again! ). I bought my first Apple II in January 1979 and I have used only Apples since, so you can say that I am a dedicated Apple user. 1 watched as all the new versions of the Apple were released, but nothing could sway me from my old Apple (without the Autoboot Rom). I always enjoyed the way it started up in the monitor when it was turned on, no grinding disk noises for me. But now this has all changed with the release of the Apple Ilgs, let me explain. Through the years of using my computer I acquired an interest in music ~ I started with the Mountain Hardware Music System which entailed two cards and allowed you to connect to your amplifier. The basic input system used a light pen and allowed you to enter notes by pointing the pen at the screen. This was fine if you had 6 months to spare to enter one song! Somehow I managed to enter quite a bit of music over the years, mostly original songs (if you could call them songs7). Well then along came MIDI which is the standard interface for Musical Instruments. This opened up the world of Music to computer users and vice versa. Now it is possible to play back tunes, stored on your computer, on a musical instrument (mainly keyboard oriented at present). You can create your own songs and enter it on your computer even if you can’t play a note. This is why I weakened and purchased an Apple IIgs - it’s got a built in synthesizer and using the mouse to input your notes it now takes only 2 or 3 days to enter a complete song. Lets hear it for technology. Well I hope this has not bored you too much and if anyone is interested in knowing more about MIDI and computer software, then I’ll write some articles in forthcoming issues for you. Please let me know! I haven’t quite filled a whole page, as ordered, so I’ve stuck the Treasurer’s Notes in the space left and it fits perfectly! This editing is fun. { Treasurer’s Notes ] by Eric Conolly Finances are starting to build up nicely after our large expenditure in purchasing the BBS equipment. We currently have $1,400 in the bank, but before you get too excited we have a couple of bills to look after. The 5 Meg Hard Drive for the BBS is $400. This has been purchased at Apple staff discount rates and should be received before the next meeting. Stock in the trading table has diminished somewhat over the past 6 months and we will need to allocate about $600 to restock. We will also have to look at purchasing a printer shortly as we are still using Graham's printers for the trading table, the BBS and of course the newsletter. APPLE-BUG <5> June 1987 C BBS Report ] by Graham Black The on-line games, Stock Market, Casino, and the ’Land of Spur’ are increasing in popularity. As the funds become available, we will improve these areas of entertainment. There has been a Fee introduced to Non-Financial] Members of Apple-Q, to allow them access to the system. As of 19th May, they are required to pay $10 till the end of May 1988. This ensures that only Financial Members will gain Full Access to the system. This fee will entitle the user to Associate Membership, with no voting rights, and they will gain access to boards 1- 6 and the Games Machine, only. {( Secretary’s Notes ] by Vince Crosdale June, one of my favorite times of the year, the time when the exam timetables are posted on the notice boards at QIT. I am sure that many of you out there would feel this way as well. But we can’t let such trivial matters as exams worry us, we have a newsletter to do. The month of May has been a busy one for certain members of the Executive Committee, in particular Bernie Benson. Bernie has been working like the proverbial Trojan Horse in a bid to prepare a Constitution for the club to allow for incorporation. At the Special General Meeting on the 18 May, it was voted unanimously that the club proceed with the matter of incorporation. Many thanks must go out to Bernie for an excellent piece of work in the preparation of the new Constitution. There has been a regular flow of mail into the club over the past month, containing the usual advertisements and a number of letters from new members, current members and non-members. We have endeavoured to answer all requests, but if you feel that you have been missed out, don’t despair, we will get around to you in the near future. There have been a few new magazines arriving and interested people may obtain these from Richard. Thanks must also go out to Pat Bridges for her donation of several magazines to the club. There were quite a number of magazines in the box and we are very grateful for this donation. . A matter that has come to the attention of the Executive Committee during the Open Day on the 17th May, was a member selling disks at the meeting. Now we do not frown upon members selling goods at the meeting, but in relation to the goods being ’brand new’, we feel that something should be said. The selling of goods at the meetings, that is, second hand goods, is welcomed by the Executive Committee. However at the May meeting, one of the members was selling boxes of disks that were brand new. Now, this is in direct competition with the Trading Table, and the Trading Table is the clubs only major source of income. We would like it to be known that we will sell new items through the Trading Table for members, but this is the only way that brand new items such as disks may be sold at the meetings. To compound the matter, a certain gentleman at the meeting, who is not a member of the club, approached the Trading Table after the offender was asked to stop selling the APPLE BUG <6> June 1987 disks, and proceeded to advise the Committee on the legal aspects of selling items, how the club should be run and how the Education Department. was kind enough to allow us to use the premises, and that he was from the Education Department, and therefore he was entitled to tell us how our business should be conducted. Well sir, I would like to inform you that we have been in touch with the Hooper Centre over your little outburst, and we have been advised that we may eject you from the Education Centre next time you decide to air your opinions about the running of the club. Unfortunately, your status as a lecturer at Queensland University gives you no right to come to the meetings and inform the Executive Committee on how to operate the club. It also gives you no right to place yourself in a position where you feel as though you have the power to stop the club from using the Hooper Centre. The people who allow us to use the Hooper Centre have no knowledge of you, nor do they believe that you have any right to advise the club on its operations. Therefore, we would like to inform you, that if you wish to have a say in the operation of the club, then please pay your membership fees as everyone else does. Otherwise, we would like to ask you to please keep your comments to yourself, and leave the operation of the club up to us as we leave teaching students up to you. I trust that Doug will show you this. Another problem from the meetings. At the last meeting a number of people were approached about a lack of a membership card on their machines. A large number of people stated that they had ’forgotten’ their membership cards. Therefore, we ask that any member who attends a meeting and forgets their membership card, would they please come to the Trading Table and obtain a slip of paper to place on their machine for the duration of the meeting. We will ask for your membership number and validate your current membership. This measure has become necessary due to the large amount of people attending the Open Days and the number of members being inconvenienced by non-members having their equipment in the Centre. We would also ask all members and visitors attending the Open Days to please sign the attendence book provided at the entrance to the Hooper Centre. Our powerboards are disappearing. This is causing a large deal of concern amongst the Committee as these powerboards are extremely expensive. Therefore, we ask that any one who takes a powerboard for their use, leave their name, membership number and a $2 deposit when taking one of the clubs powerboards. The $2 will be refunded to you when you return the powerboard, or you can find another person who will sign for the powerboard. The powerboards cost the club approximately $15 each, and of late have been disappearing at a rather alarming rate. The club is looking for a new source of Public Domain Software (PDS). The present collection of PDS is getting extremely out of date and we would like to start updating the clubs PDS library with new disks. If anyone knows of a source of PDS or has any thoughts on the sort of PDS that the club should try to invest in, could they please let us know. Well that is about it for this month. Again I would ask members for contributions to the newsletter. Many thanks must go oul to Brett Dutton for the excellent articles that he has been providing for the newsletter. Remember, contributions may be sent to us via mail, the BBS or left at the Trading Table on Open Days. All care will be taken and disks sent in will be returned. So until next month, Good Computing. APPLE-BUG <7> June 1987 { Software Library ] Softdisk Volumes: The files are divided into sect required for the particular app represents the file type. i.e. B=B section is seperated by a stri string of =’s. ions, and the files in each section are lications. The prefix before each file name inary T=Text A-Applesoft T=Integer. Each ng of -’s and each volume is seperated by a Volume # 43 - Disk 1 Side 1 : FREE SECTORS = 9 (2.25k) A HI A HELLO A MENU B SOFTCOVER B SIDE NUMBER 43 B S.D. RESET MSG B PACK/UNPACKER A ACES UP II A ACES UP II. INST A ACES UP II.PROG B ACES UP II.PAC B SOUND1 B PACK/UNPACK B SUPER-SHAPES T ABOUT.ACES UP II A RAINBOW START A RAINBOW GAME B PICTR. SQUARE. PAC T ABOUT.RAINBOW GAME A CARDIO-PULMONARY RESUSCITATIO T ABOUT.CPR A BEGIN B INTRO. PAC B FIRST. PAC B OUTSIDE. PAC B INSIDE.PAC B LAST. PAC B FOILTHEORY. PAC T ABOUT. FOIL THEORY A GRAPH MSTR T ABOUT. FLEXI-GRAPH A RHYMER T ABOUT. RHYMER A CUSTOM CHARACTERS T ABOUT.CUSTOM CHARACTERS A MAKE DISK DOSLESS.DOC T ABOUT.MAKE DISK DOSLESS CATALOG SORT V2.0 Volume # 43 - Disk 1 - Side 2: B MAKE DISK DOSLESS ABOUT.CATALOG SORT V2.0 FREE SECTORS = 16 (4k) A HELLO B SIDE NUMBER 43 B S.D. RESET MSG A SOFTDISK PRESENTS B LOWER MUSIC B LOWER TEXT B PLAYER T STASH HI T RESTORE LOW A RECON T RECONT A CONTENTS MAP T CONTENTS MAP.T A NUMBER 43 COVER B COVER.NUMBER 43.PAC APPLE- BUG B COVER ANIM R T FEATURES21 T T RECIPE OF THE MONTH i T SOFT SPOUT T A Q & D SOFTDISK SCANNER B T FEATURES22 T DOS ERROR MESSAGES 4.5 T DOS ERROR MESSAGES 10--13 A DOS TUTORIAL MENU B DOS DEMO 1.12 T BITS TEXT.12 T FEATURES23 T NUMBER THEORY T THE GCD OF TWO INTEGERS T NEXT MONTH as haga Side 1 Volume # 43 - Disk 2 A HELLO B B S.D. RESET MSG A GRAPHIC FANTASIES 4 Prmmomw A ASTRONOMY MENU A VENUS A CONFIGURE A FULL MOONS A ALMANAC A SEE STARS A COMET A CHINESE NEW YEAR B TABLE.B HAwU>> >>> >> A ALFREDO’S TRANSPORT TROUBLE > FREE SECTORS = June 1987 PACK/UNPACK SOFTGAB QUOTE OF THE MONTH WHEN YOU GET AN ERROR Q & D RWTRACK DOS ERROR MESSAGES | 3 DOS ERROR MESSAGES 6 9 DOS ERROR MESSAGES 14 15 DOS TEXT.12 TEXT.DOS DEMO 2.12 TEXT.BITS DEMO 1.12 MATHEMATICAL REFLECTIONS THE EUCLIDEAN ALGORTTHM THE LCM OF TWO INTEGERS GcD 91 (22. 75k) SIDE NUMBER 43 GF.OBJ STARS GAS GIANTS WINTER SOLSTICE MOON CONFIGURATION MARS SS FEASTS CHARACTER .R STARDATAFILE ALF . PROGRAM. A2 LOWER MUSIC B STASH HI Volume # 43 - Disk 2 ~- Side 2: A HELLO B B S.D. RESET MSG A SOFTDISK PRESENTS B B T T FREE SECTORS = 23 (5.75K) SIDE NUMBER 43 LOWER TEXT PLAYER RESTORE LOW APPLE-BUG <9> June 1987 A RICH & FAMOUS T RICH & FAMOUS DATA A AD.ONE STEP BEYOND B PM B PD A AD.PRINCESS & VALLEY OF FIRE B PVF.1 B PVF.2 B PVF.3 B PVF.4 B PVF.5 T FEATURES41 T BACK ISSUES T SOFT REWARD T SOFT DEAL T HELP THE CAUSE T ABOUT HARVEST T ABOUT PIPELINE T ANNUAL SUBSCRIPTION A FORMS .MENU A ORDER. BLANK A SIGN-UP. FORM T FEATURES42 ADVENTURE REQUESTS BUGS & STUFF HARDWARE AID REQUESTS HARDWARE HINTS PAL CORRESPONDENCE T ADVENTURE HINTS T T T PRINTER HINTS T PRINTER REQUESTS T T T BBS INFORMATION AHA T PRINT SHOP TALK PROGRAM REQUESTS #1 T PROGRAM REQUESTS #2 REVIEW - FAMILY ROOTS T REVIEW - LIFESAVER REVIEW - XYPHUS B PS.GA.CUB WOLF B PS.WELCOME MAT B PS.KEY B PS.CASTLE B PS.HEART B PS.FUNNY MAN B PS.HAPPY DOG B PS.WATCH B PS.FACE B PS.CAMERA SLR A PIPELINE B PIPELINE. OBJ BEXTRA HCOLORS by Brett Dutton An extra six HCOLORs can be obtained on the HIRES screen by ’miving’ certain standard HCOLORs. This is done by plotting different coloured horozontal lineson alternative rows. Except black and white, all the other HCOLORs can be ‘mixed’ together. eg. Mixing purple and red will give you a magenta colour. 20 REM *** HCOLOR MIXER *** 30 HOME : HGR 40 READ A,B : IF A = 8 THEN END 50 HCOLOR = A: FOR I = J TO J+8 STEP 2 60 HPLOT 0,I TO 279,I : NEXT 70 HCOLOR = B : FOR I = J+1 TO J+9 STEP 2 80 HPLOT 0,1 TO 279,1 : NEXT 90 VTAB 22 : HTABI : PRINT "HCOLORS"; A; "AND";B 100 PRINT "PRESS ANY KEY TO CONTINUE"; 110 GET A$ : J = J + 12: GOTO 40 120 DATA 1,1,2,2,3,3,4,4,5,5,6,6,1,2,1,5,1,6 130 DATA 2,5,2,6,5,6,8,8 APPLE BUG <¢10> June 1987 ( Feature Article ] by: Brett Dutton BEATING THE RS~232 BLUES A serial interface should be the simplest way to connect two pieces of computer gear together. Unfortunately, RS-232 complicates matters. Only two pieces of wire are needed to allow one computer device to talk to another, and three if you want a two-way conversation. So you would think that hooking together computer equipment with serial interfaces would be easy - provided, of course, that the various equipment manufacturers had adopted a standard for their interfaces. And herein lies a problem. The ‘standard’ which was adopted for serial interface was known as ‘RS-232’. RS-232 is a standard of the American Electronics Industries Association, and was originally intended to interface between ‘Data Terminal Equipment’ (DTE - in other words a computer ‘dumb’ terminal) and ‘Data Communication Equipment’ (DCE - equipment which facilitates communication to a remote computer, like a modem). The standard specifies the electrical characteristics of the interface signals, along with the shape and pin assignments of the connectors to be used. In addition there are certain other conventions which go along with this standard, like the commonly used data rates and formats. Now, although it’s possible to borrow the electrical and timing conventions from this standard, many aspects are ambiguous. As mentioned above, RS-232 specifies two different ‘sexes’ of equipment, terminal equipment and communications equipment, each with its own sex of connector, and their own connector pin assignments. But the standard is now being applied also to computers, printers, digitising tablets, speech synthesizers and so on, which don’t fall conveniently into the catagory of either sex. Consequently any piece of equipment has more or less arbitrary sex assignments. Furthermore, RS-232 contains specifications for using its connectors and signals for a large number of applications. Since today’s equipment needs only the simplest of such arrangements, most RS-232’s features are not used, and in fact merely add to the confusion as manufacturers arbitrarily select the few features they need for their interfaces. OK, the fact that the interface is somewhat arbitrary on any piece of equipment would be compensated if the equipment. manual told you how it worked. Not the case. In fact the description of how the RS-232 interface works is almost universally the worst described part of the manual, ranging from extremely ambiguous to downright wrong. In the following I am going to describe the theory of how RS 232 is supposed to work. If anyone is interested and very keen I will forward a document that describes a test unit that will patch any two devices together, and monitor what they are saying. So if you wish to build one or borrow the principles to understand how to test and interface by some alternative method, send your request to:~ Brett Dutton c/o The Registrar Apple-Q: the Brisbane Users’ Group P.O.Box 698 Redcliffe 4020. APPLE BUG <11> June 1987 The Basis of a Serial laterface There are many possible ways to make serial communications ‘channel’; RS-232 is just one method. Let us examine serial interfaces in general, and see how RS-232 implements the various features involved. I should point out here that many of these features are not strictly a part of RS-232, but are conventions which are used with it. The best way to declare something as a ‘convention’ is by referring to data on the ICs used to implement RS-232 serial interfaces, namely the ‘UART’ which formats the data (such as the National 5303 and similar), and the ‘line driver’ and ‘receiver’ which actually send and receive the electrical signals on the serial cable (National IM1488 and 1489 respectively). Suppose we are dealing with the simplest type of interface, one in which there is a ‘sender’ and a ‘receiver’ such as may be the case where a computer sends data to a line printer. Two wires connect the two devices, one wire being ‘Ground’ or zero volts, the other wire carrying the data. Ones and Zeros The first task is to decide how to represent binary ‘one’ and ‘zero’ as voltages. A TTL logic IC regards a voltage less than 0.4 V as a logic zero, and a voltage greater than 2.8 is logic one. A TTI. output is not, for various reasons, suited to sending data down a long wire, so RS~-232 does things differently. A ‘zero’ is represented by a ‘high’ voltage between +2 V and +12 Vv (for some reason called a ‘space’), while a ‘one’ is represented by a ‘low’ voltage between ~-3 V and -12 V (also called ‘mark’). The range between 3 V and +3 V is undefined. Next we must decide in what order and with what timing the bits are to be sent down the wire. RS-232 calls the unit of data transmission a ‘character’, even though the data may not actually represent a character. A particular device may be set to transmit or receive 5, 6, 7, or 8-bit character, with seven being the most common (because seven bits will represent the entire ASCII set of 128 characters), and 8 the next most popular. These characters are sent least significant bit first. Using the scheme as I have so far described it, the letter ‘B’, which is ASCII $42 Hexadecimal, or 66 Decimal, would appear on the line as (see figure 1): High low high high high high low (7-bit code) Figure 1. The letter ‘B’ (hex 42) represented as a sequence of voltage levels, as used by the RS-232 devices. How does the receiver know when a particular character starts? We could use a_ third wire to signal that a character is starting on the second wire. This is a form of ‘syncronous’ communication, and is not used with any personal computer equipment. Instead RS-232 has a way of telling the receiver that a character is starting. It works as follows. Start Bit Suppose the receiver receives the above letter ‘B’. Normally the APPLE-BUG <12> June 1987 communications line sits at ‘mark’ or low. Along comes bit one, which is a high, and immediately the receiver knows a character is coming in. Now, assuming that the receiver and sender are set so they agree to how long each bit is, the receiver will then be able to recognise a high, then a low, then another low, and so on until the ‘B’ has been received. However, suppose that instead the letter ‘A’ was sent, which is $4] Hex, and therefore is represented as in Figure 2: Low high high high high high low Figure 2. The letter ‘A’ (hex 41) represented in RS:232 voltage levels. This time, by the time the receiver finds out something is happening, it’s already on the second bit! And what if you had a character consisting only of lows? The way around this problem is to prefix every character’ with a ‘start’ bit, which is invariably high. Stop Bit This still leaves one problem. Suppose we send several hundred characters in a row. It would be unreasonable to expect that the sender and _ receiver agree as to the time-per-bit to such great accuracy that. they would still be in step after so many bits. To overcome this each character is suffixed with one or two (according to how the devices are set) ‘stop’ bits, which are always low. After each character we always have a _ low-to-high transition which can be relied upon to keep the two devices in step. Notice that there is nothing particularly special about the start and stop bits. They look like any other bits except there is always a low to high transition at least once per character, and it’s between these two bits. I point this out because it means, for example, that if you are sending serial data to a printer, if the signal is momentarily disconnected (transmission continuing but reception interrupted) then upon reconnection the printer will probably not be able to interpret the incoming stream of highs and lows. The printer will be confused until the next pause in transmission, unless the combination of received characters enables the printer to determine where the stop-start location is. Transmission Speed: (Baud Rate) Naturally, both sender and receiver must be set to the same nominal communications speed. This speed is measured in bits-per-second, a unit also known as the baud. (One bit per second is one baud.) Commonly used baud rates are: 110 and 133 (for Selectric terminals, for example), 300 baud (modems communicating via telephone), 600, 1200, 2400, 4800 and 9600 baud. Some devices also communicate at 19.2k, 38.4k, and even 76.8k baud, but such are rare. Parity An embellishment which is occasionally seen is the use of ‘parity’ as an APPLE-BUG <13> June 1987 error checking method. In a seven bit code, for example, an extra bit may be added after the last bit (but before the stop bit). The sender counts the number of ‘one’ bits in the character, and if the answer is even it sets the parity bit to ‘one’, if not it is made ‘zero’. (This is the even parity convention. There’s an equally little-used odd parity convention which makes the parity bit ‘one’ for an odd total.) When the receiver gets the character it does the same arithmetic and compares it’s answer to the parity bit received with the character. If it has the same answer it knows all is well; if the answer is wrong an error has occured somewhere. for example, suppose an ‘A’ is transmitted (seven-bit, even parity). This would be represented as in Figure 3. MX... DATA on) START (THERE MAY BE NO WAITING) Figure 3. Representation of the letter ‘A’ in seven-bit even parity code. Note that a ‘l’ is a low voltage and a ‘0’ is a high. The line normally sits at low or ‘1’. You can probably see that this scheme cannot show where the error occured or how to fix it, nor does it signal double errors. It is basically a low-overhead warning device. In fact parity is generally ignored, since most personal computer equipment is not operated in electrically noisy environments where such errors are likely to occur, and in any case such equipment has no convention for requesting that the sender resend the faulty received data. (often the receiving device may be set to expect the parity bit but not use it.) However, I have included this description so that you know what parity is when the equipment has a switch to select or deselect its use. Lots of Options! As you can see, even this far there are plenty of options to choose from. In a typical device many of these options may be switch selectable, usually miniature DIP switches inside the box, or perhaps soldered jumpers. In some cases, such as terminals and computers, some of these features may be programed from the keyboard or from the software. . So there are plenty of ways in which your two little darlings won’t be able to talk to each other! But wait, there’s much more! How Many Duplexes? Although not strictly of direct concern in the RS- 232 interface, some equipment, particually terminals and modems, provide a ‘Full/Half Duplexes’ switch. ‘Full Duplex’ means that when the terminal transmits a character to the remote computer the computer immediately echoes the character back to the terminal, whereupon it appears on the terminal screen (or paper, if a teletype). If there is no echo then the character you typed will not appear on the terminal’s screen. This is a kind of insurance method to let you know that the computer is listening. ‘Half Duplex’ means it is assumed that the computer will not echo the APPLE-BUG <14> June 1987 characters from the terminal, and thus the terminal puts the typed characters on the screen whether or not the computer is awake. The suprise comes if you have your terminal (or modem) set to Half Duplex, and the computer you are talking to, echos the characters. Then if you type ‘FRED’ you’1l see ‘FFRREEDD’. Not so Fast! A commonly needed feature is the ability to tell the sending device to slow down. I don’t mean to send at a lower baud rate, but rather to pause for a moment. A typical situation where this occurs is in slow printers. When the carriage reaches the end of the line the printer must tel] the sender to wait until the carriage returns before sending more characters. Such a signalling system is known as ‘handshaking’. Typically this is implemented by adding an extra wire to the interface cable. The receiver maintains this wire at a ‘high’ signal level while it’s OK for the sender to send, pulling it ‘low’ to tell the sender to halt the flow of data. Sometimes an interface will have handshaking lines both ways, so that either device can halt the other. A complete two-way interface would consist of two data wires, two handshaking wires and ground - a total of five wires. Most RS-~-232 hook-up problems occur because one piece of equipment needs some of these signals which the other does not provide, or because the wires in each piece of equipment are not connected to the corresponding pins in the interfacing connectors. Not so Fast Type Two A quick note here that on some intelligent printers handshaking is carried out using a method called ‘X-on, X-off’. Instead of a separate handshaking wire, the printer has a data output wire (normally printers only recieve data). If the printer wishes to halt the sender the printer sends a control character to the sender (usually control-S, hex 13, which is also known as ‘Direct Control 3’). Subsequently sending the same character will restart the data. Note that this is the same character which you use in Apple (and CP/M) to stop and start a continuous display to the screen from the keyboard. Handshaking and Buffers, etc How necessary is handshaking in practice? A major sore point in the small computer industry has been the need for handshaking in printers. The Epson MX-80, for example, was available at one time with a serial interface known as 8141. This interface could only remember a maximum of two characters as they arrived from the computer. Since the ‘line-feed’ time exceeds the time of two characters, even at the slowest baud rates it was necessary for the interface signal to halt after each Jine. The standard Exidy Sorcerer and the standard Apple printer interface board do not have any handshaking inputs, and consequently it would be impossible to make this combination of equipment work serially. (This particular problem rarely comes up since the MX-80 has a parallel input which is usually used. The Sorcerer has a parallel, and the Apple has various parallel cards available.) A solution to this dilemma which is finding widespread adoption is to incorporate a ‘buffer’ into the serial interface. Such is the Epson 8145 interface, which has a 2000--character (approx.) buffer. Since the MX-80 chugs along at 80 characters-per-second (cps), if the computer transmits at 300 baud (30 cps) the buffer is normally virtually empty. At line feed time the buffer fills up a little as the computer continues to transmit. But the MX-80 catches up on the next line. There is thus no need for handshaking. You can, however, get into trouble if the computer sends a large number of form-feeds, APPLE-BUG <15> June 1987 which take a long time. Wires and Connectors and Stuff The connector used with RS-232 is known as a ‘DB25’, which has 25 pins in the male, and 25 receptacles in the female. But why 25 pins? RS-232 was endowed with a pile of features not now used, an these were implemented using most of the 25 pins. Now very few pins are used. The extra provide two oportunities for confusion and problems, however. One problem is that with such a profusion of pins it can be difficult to figure out which ones you are supposed to use for your application. The extra problem area is that with all those extra tantalising pins available and otherwise doing nothing, many manufactures use the ‘spare’ pins for other purposes. Exidy uses them for the cassette interface. IDS, in their paper tiger printers, use the same DB25 for both serial and parallel interfaces. That’s fine except that if between such units you use a cable with too many wires implemented (and this can easily be the case if you use a standard RS-232 cable in a set-up which does not use handshaking) then you are likely to blow something at one or both ends! The pins which are commonly used are shown in Figure 4. Note that the naming convention can result in a variety of confusions. If the equipment is masquerading as a DCE the manual may tell you that, for example, pin 2 is ‘Transmitted Data’, which strictly speaking is an input. However the manual writer may not know this and instead call it ‘Received Data’, intending ‘Received’ in a looser sense. ‘Official’ Pin DTE DCE Signal Name Abbrev No. ‘Terminal’ ‘Modem’ Components Protective ground PG 1 — aa Optional Signal ground SG 7 - - Necessary Data: Transmitted data TxD 2 Out In Received data RxD 3 In Out Handshaking: Request to send RTS 4 Out. In ) Basically Data terminal ready DTR 20 Out In ) same use Clear to send cTSsS 5 In Out ) Basically Data set ready DSR 6 In Out ) same use Connector Sex: Male Female Figure 4. Table of signals, pin assignments, etc Fighting Back The first thing to do before connecting anything is to make yourself a chart like the one in Figure 5 for each piece of equipment you may have to connect together. This is especially important if you are involved with many different units. To connect two pieces of equipment becomes quite an easy task if you have a chart like this for each piece of equipment. APPLE-BUG <16> June 1987 PIN SIGNAL SIGNAL IN/ OPEN ABBREV. _ NAME COUT, OK? COMMENTS. EQUIPMENT TYPE: CONNECTOR SEX ON EQUIP: DATE: Figure 5. Interface chart to save headaches. The point to this chart is that for each of your pieces of equipment it serves to collect titbits of information you will glean from the manuals, the schematic and so on. You end up with the info in the same format for each unit, where it can be simply compared to give the best idea of how to wire things up before you blow anything, and before you have the frustrating experience of having the system not work. If handshaking lines are provided , try to find out if they actually do anything, or if they are dummies. For example, one printer may have an output which signals the sending computer to halt. Another printer may claim to have the same handshaking output, but it is actually internally wired permanently high, and is provided merely for the supposed compatibility to a computer which may need such an input so as not to halt. Got that?! Wiring Up The Cable You will notice that if one of your units is a true NTE and the other is a true DCE then a standard cable (pin 1 goes to pin 1, 2 to 2 and so forth, which is called a ‘straight through’) will work. You are unlikely to see this situation very often, which is something you should know before you buy such a cable made up (they’re likely to be expensive ready-made), or before you get convinced by the salesman that the printer hook-up is trivial. So you decide to wire your cable. First, of course, you must obtain the appropriate sexes of connectors to mate with what you have on the equipment, APPLE-BUG <17> June 1987 and a cable with sufficient number of conductors. If it’s over 20 feet you may wish to use shielded cable, but I’ve heard of unshielded, up to several hundred feet. Next, no matter what the equipment. involved, wire pin 7 to pin 7. If it’s a straight-through you are making, then go right ahead, 2 to 2, 3 to 3, etc. The next-most-delightful situation is where the two units are of the same sex and need no handshaking lines. For the data lines simply wire 2 to 3 and 3 to 2. If handshaking lines are needed then determine which handshaking outputs actually mean something (as opposed to the dummies). Then connect these to the handshaking inputs of the opposite units. You may have a sender which is not sending to a receiver which does not need to halt the sender. If this is the case you need to decide what to do with the sender’s handshaking input. In some units it can merely be left open (unconnected), and this is seen as the same as ‘high’. On other units open is taken as a ‘low’ and halts transmission. The handshaking input may be wired permanently high by jumpering it to a handshaking output on the same device. This is normally done inside the plug on that unit’s end of the cable. Figure 6 shows some typical cable configurations. 2 3 oe 6a. The simplest cable, 4 -\% af 5 opposite sexes, no 1 seveseusremecaene mamma handshaking. 20-/ \ 6 5 -\* #/- 4 6 -/ \- 20 (# CHOOSE 1 OF 2) 6b. The next simpliest cable 6d. Joining same sexes with DCE to DCE or DTE to DTE, handshaking (one possibillity). and no handshaking. o--/8 (# SOMETIMES ONE OR TWO OF THESK MUST BE OMITTED. ) 6c. Cable to join opposite 6e. Joining opposite sexes, sexes with handshaking. with defeated handshaking (’Standard’ straight-through at both ends. cable). Figure 6. Some typical cable hookups APPLE-BUG <18> June 1987 The Initial Hook-up Armed with the appropriate (we hope) cable, plug in and see if it works! It probably won’t, so refer to Figure 7, which is a summary of al] the things to check to make the two pieces of equipment compat ible communicators. 1. Number of bits per character: 5, 6, 7 or 8. 2. Number of stop bits: 1 or 2. 3. Baud rate: 110, 150, 300, 600, 1200, 1800, 2400, 9600 or other 4. What to do with Parity: On transmission: No parity, Even parity, Odd parity, Parity bit set to 0 or Parity bit set to l. On reception: No parity expected, Ignore parity, Expect. Odd, or Expect Even. 5. Full or Half Duplex. 6. Make sure machines are online if they have the ability to be offline. 7. A rather rare final item which can cause problems is an option on a few machines which allows of the polarity of the data signals and/or handshaking signals. You should set these to: Negative Mark for the data . lines, and handshaking lines should indicate OK to proceed with a high level, STOP with a low level. 8. Any wore problems and you'll have to get in contact with Apple Q to get the instructions for the RS -232 checking device. Figure 7. Quick check list A Test Box to Defeat All Problems So perplexing are some RS-232 problems which T have encountered that 1 highly recommend obtaining a test unit of some kind if you are going to be involved with many such situations, or contact Apple Q for the details of a device which is designed to handle these problems, and which also permits quick patching together any trial interface configuration. Unlike commercial units, it will even enable you to determine the inputs and outputs of a completely unknown interface with no documentation. 0000000000000 ( Advertisements ] FOR SALE —> Contact: Graham Black at the Trading Table or ph.(07) 883.1525 NetComm manual modem 3+12 $285 (new) Speed Demon (speeds up the apple 3.5 times faster than normal) $ 500 Roland DXY-800 Plotter (8 colour) includes many pens and paper $1050 Alf Synthesizer + amplifier + approx. 30 disk of music (best offer) FOR SALE -—> Contact: Chris Taylor - ph. (07) 376-6590 DOS - Applesoft - assorted Machine Language Manuals $10 each Slimline Disk Drive $130 Drive controller $40 Green Screen Monitor $130 80 col.card (J[!') $45 Auto-ice printer card $ 70 APPLE~BUG <19> June 1987 FOR SALE —> Contact: Brodie Thiesfield of Lowood on ph. (075) 86 1618 Apple }[{+ disk drive monitor speach card colour card. Can be viewed at Redcliffe 45 disks plus manuals. $820 FOR SALE —> Contact: Vince Crosdale on ph. (07) 351-3090 Enhanced Apple //e 128k, two disk drives, monitor, parallel card, RGB card, manuals many disks included. $2200 THIS SPACE IS RESERVED FOR YOUR ADVERTISING !!1! Advertising Rates:- FREE to all Financial Members C Special Discount Offers |] The following Dealers, have offered a cash discount on all Apple products to FINANCIAL MEMBERS ONLY, on production of CURRENT membership cards. Please note: Members MUST produce their current membership cards if they wish to take advantage of this offer. DELSOUND ELECTRONICS 1 Wickham Terrace (corner Wharf Street), Brisbane telephone: (07) 839-6155 ask for John COMPUTER ORCHARD 671 Gympie Road, Chermside, Brisbane telephone: (07) 350-1255 ask for Scott THE BYTE CENTRE 49 Park Road, Milton, Brisbane telephone: (07) 369-4099 ask for James Donegan COMPUTER CITY 600 Wynnum Road, Morningside, Brisbane telephone: (07) 395-6816 ask for Peter Newland APPLE-BUG <20> June 1987 Rec: ..... wee & ENposee 33 Ese Membership Number ... Apple-Q: the Brisbane Users’ Group MEMBERSHIP RENEWAL Membership to Apple-Q is on an annual basis from the month that you join. All members on our books are required to note any changes to their personal details and forward to the Registrar upon renewal of their membership. MEMBERSHIP FEES (] $20.00 Adult and Family memberships { ] $12.00 bona fide students under the age of 21 {] $12.00 pensioners upon production of pension card (at the discretion of the Executive Committce) AE OO OOO OHO OK Membership Renewal Form Business. telephone: (oie: ):s:0:s:ceiwreeiceiace were evecesevevereriamiere eteveeiernre avave I hereby declare that the above details are true and correct, and agree to abide by the Rules and Regulations of the group. Signed: ............ee ee eeeee Please complete these details to allow our records to be checked. DO NOT use this form for an initial membership application. Forms for that purpose may be obtained fram the Registrar or the Secretary. THIS FORM SHOULD BE COMPLETKD AND RETURNED WITH FEE KITHER: at the next Open Day -or