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Need help identifying pins on an old PS/2 interface IC

Chris Woelkers
Prodigy 10 points

I have an old keyboard, an IBM Model M produced by Lexmark to be exact, that I am trying to convert from PS/2 to USB. Instructions for doing this by using an active PS/2 to USB converter are available elsewhere but not for this specific model which uses a different PS/2 chip than the others shown in the instructions. What I need is either some help in identifying the PS/2 clock and data pins or a datasheet, for the PS/2 interface chip on the PCB.

I have already looked around on the Internet and TI's site but have found no clues so far. Here is a pic of the IC.

The markings on the IC are: 52D0ETK (or 52DOETK)  and   2392161-60425

One of the PS/2 wires goes into the IC at pin 2 and 3 while the other is connected at pins 5 and 12. Both have a capacitor going to ground and a resistor (the blue package) going to VCC(+5 VDC) connected in parallel.

Pin 7 is connected to GND and pin 14 is connected to VCC.

Besides the VCC, GND, PS/2 Clock, and PS/2 Data, it also has 8 pins which all seem to connect to the primary controller chip for the keyboard which most likely are D0-D7 or D0-D6 with a selector or modifier bit connection.

Sorry if this might be in the wrong forum. Please move it if it is.

  • 0
    TI__Genius 16430 points

    Chris,

    Unfortunately the device is 10+ years old and is a custom device manufactured for Lexmark when it was actually still part of IBM.  Any infomration on the device will need to come from Lexmark.

     

  • 0
    TI__Genius 16430 points

    I received what may be a better answer for you - no gurantees as this is coming from some ones deep memories:

    ...the device referenced is a simple TI 7406 buffer. This is a really old keyboard, in that we eventually removed this isolation, and drove the clock & data directly from the controller... 14 pins - power & ground for the IC, and six (I seem to recall they were inverting) line buffers. One buffer in each direction for clock & data (4 total), with the remaining two buffers used to drive a couple of the LEDs for CAPS and NUM lock indicators.

    Not sure if this helps or not, but thought I would share it for what it is worth.