PAK-V1a PS/2 coprocessor

[srob]

Am building a controller that uses a PS/2 keyboard to input data (the one I using at the moment is a Fujitsu E105). For ease of programming I wish to the above coprocessor.

Have built the circuit as shown in the manual, with IMODE=0V, ENABLE=5V and ENABLE2=0V.

Have taken the DATA to pin1 of the keyboard, CLK to pin5 and 5V to pin4 and GND to pin3 of the keyboard.

The Tx I have taken to a 16F73 running at 20MHz. My problem is that I get no data into the coprocessor, the CLK pin appears to be tied to 5V, and the DATA pin to GND!

When I remove the keyboard DATA input to the processor I get the correct CLK and DATA outputs from the keyboard and when I connect the DATA to the processor whilst running it works fine. But as soon as I switch off and on again the same problem occurs. Does anyone have this problem, or solution?

Thanks

[Ron Marcus]

<When I remove the keyboard DATA input to the processor I get the correct CLK and DATA outputs from the keyboard and when I connect the DATA to the processor whilst running it works fine. But as soon as I switch off and on again the same problem occurs. Does anyone have this problem, or solution?

Thanks>

Look at the tris registers on the PIC. They should be set to input on power up. There is a reset sequence that the PC sends to the keyboard on startup that you can try, but it souncs like it doesn't need it if it fires up correctly on it's own. Remember that the link between the PS/2 and the PC is a quasi I2C format, and the two valid states are input(high impedance) and low only.

Ron