I've got a little project and I could use a bit of help.
I have an old load management unit that has the option to add an external I/O and display board to convert it into a portable testing unit, and I was able to locate and borrow one of these portable test units long enough to reverse-engineer both add-on boards and make a schematic of same.
I'd like to make an SMT version of the add-on board(s) and possibly update the circuit to eliminate the need for the 12V supply (driving the LED displays). However, a couple of the ICs used, in particular the 8279 display / keyboard driver and the two HM-6561 RAM ICs (which are a puny 128 nybbles each!) may be hard to get new these days, and I wonder if something like this could be adapted to an Arduino controller?
There are four connectors on the combined boards: One for the 4x4 keyboard matrix, one for the external connection to the unit, and two to plug in where the 6561 RAMs reside on the unit's CPU board (one connector provides the address, lower nybble, and control lines, the second one provides the upper nybble).
I've attached a copy of the schematic and the data sheet for the 6561 RAM ICs. I figure that whatever I end up using should mimic the timing of the 6561s, hence the data sheet.
I have an old load management unit that has the option to add an external I/O and display board to convert it into a portable testing unit, and I was able to locate and borrow one of these portable test units long enough to reverse-engineer both add-on boards and make a schematic of same.
I'd like to make an SMT version of the add-on board(s) and possibly update the circuit to eliminate the need for the 12V supply (driving the LED displays). However, a couple of the ICs used, in particular the 8279 display / keyboard driver and the two HM-6561 RAM ICs (which are a puny 128 nybbles each!) may be hard to get new these days, and I wonder if something like this could be adapted to an Arduino controller?
There are four connectors on the combined boards: One for the 4x4 keyboard matrix, one for the external connection to the unit, and two to plug in where the 6561 RAMs reside on the unit's CPU board (one connector provides the address, lower nybble, and control lines, the second one provides the upper nybble).
I've attached a copy of the schematic and the data sheet for the 6561 RAM ICs. I figure that whatever I end up using should mimic the timing of the 6561s, hence the data sheet.
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