OK, now we're talking 
First of all: please cover that EPROM quartz window! We don't want that valuable code erased by ambient UV light...
I shouldn't be writing this (nor even lurking the 68kmla forums) becasue I'm on the last days of a terrible fortnight at work... but I promise to get back to this very interesting project as soon as possible -- not only for the convenient use of popular PS/2 keyboards, but because it may shed some light on the obscure ADB protocol...
Let's go with the ICs: the brain of this device is the Micro Controller, MC68L11D0 -- this is one of the many variants of the popular MC68HC11, with the following differences:
-Works on supply voltages as low as 3 V (although 5 V is fine with it)
-Has no built-in ROM (the -D0 part)
Like many other MCUs, this family may work, among others, in two modes: single-chip (code is executed from internal ROM, and most pins are dedicated to I/O functions) and extended-multiplexed mode; where data and address buses are externally accesible, and code is to be found on an external (EP)ROM chip. This version lacking the internal ROM, obviously is configured to work on this last mode. From my datasheets, it seems that this one can't go over 2 MHz.
Then there's the TC232CPE, close to a bunch of electrolytic capacitors... as the name suggests, this is an equivalent of the popular MAX232, just a converter from TTL/CMOS levels to the +12...-12 V required by th RS-232C serial port -- all from a single +5 V supply!
The EPROM is a 27C64-200DC: a mere 8 KiB EPROM in a rather slow (200 ns) version -- nothing out from the ordinary and shouldn't have that much code to investigate... anyway, this is easily read/copied on the cheapest EPROM programmer (it is socketed, isn't it?)
The remaining ICs are simple logic devices: 74LS05 (open-collector inverters), 74HC00 (quad 2-input NAND gates) and featuring the 74HC573: 8-bit latch for the multiplexed address/data bus.
Save for capacitors and resistor packs, passive components are clear -- although the exact frequency of the crystal might be critical for the interface timing.
The PCB seems to be a simple 2-layer design... shouldn't be that difficult to reverse-engineer -- as soon as I get some time, of course. I don't expect many surprises with the well known pinouts of these ICs, but another picture of the board with the ICs off from their sockets could discard any doubts...
For the general public information: the Keyboard input on your device is the older AT standard on 5-pin full-size DIN connector, but this is electrically compatible (protocol included) with the PS/2 standard, just using a 6-pin Mini-DIN.
So many hacks, so little time... :b&w:
First of all: please cover that EPROM quartz window! We don't want that valuable code erased by ambient UV light...
I shouldn't be writing this (nor even lurking the 68kmla forums) becasue I'm on the last days of a terrible fortnight at work... but I promise to get back to this very interesting project as soon as possible -- not only for the convenient use of popular PS/2 keyboards, but because it may shed some light on the obscure ADB protocol...
Let's go with the ICs: the brain of this device is the Micro Controller, MC68L11D0 -- this is one of the many variants of the popular MC68HC11, with the following differences:
-Works on supply voltages as low as 3 V (although 5 V is fine with it)
-Has no built-in ROM (the -D0 part)
Like many other MCUs, this family may work, among others, in two modes: single-chip (code is executed from internal ROM, and most pins are dedicated to I/O functions) and extended-multiplexed mode; where data and address buses are externally accesible, and code is to be found on an external (EP)ROM chip. This version lacking the internal ROM, obviously is configured to work on this last mode. From my datasheets, it seems that this one can't go over 2 MHz.
Then there's the TC232CPE, close to a bunch of electrolytic capacitors... as the name suggests, this is an equivalent of the popular MAX232, just a converter from TTL/CMOS levels to the +12...-12 V required by th RS-232C serial port -- all from a single +5 V supply!
The EPROM is a 27C64-200DC: a mere 8 KiB EPROM in a rather slow (200 ns) version -- nothing out from the ordinary and shouldn't have that much code to investigate... anyway, this is easily read/copied on the cheapest EPROM programmer (it is socketed, isn't it?)
The remaining ICs are simple logic devices: 74LS05 (open-collector inverters), 74HC00 (quad 2-input NAND gates) and featuring the 74HC573: 8-bit latch for the multiplexed address/data bus.
Save for capacitors and resistor packs, passive components are clear -- although the exact frequency of the crystal might be critical for the interface timing.
The PCB seems to be a simple 2-layer design... shouldn't be that difficult to reverse-engineer -- as soon as I get some time, of course. I don't expect many surprises with the well known pinouts of these ICs, but another picture of the board with the ICs off from their sockets could discard any doubts...
For the general public information: the Keyboard input on your device is the older AT standard on 5-pin full-size DIN connector, but this is electrically compatible (protocol included) with the PS/2 standard, just using a 6-pin Mini-DIN.
So many hacks, so little time... :b&w: