On Dec 28, 19:53, Sellam Ismail wrote: That's an odd VIA. You mean a single 6522, right? It has two bidirectional 8-bit ports, each of which has 2 associated handshake lines. Each of the bidirection lines can be set to be an input or an output, so it might seem like you have 16 possible inputs and 16 possible outputs -- but you only have 16 connections (plus 4 handshake). The only 16-bit parts of a 6522 are the timers. Timer 1 is a 16-bit counter accessed as two adjacent 8-bit bytes, and two 8-bit latches (used to reload it when it counts down to zero). Timer 2 is a 16-bit counter accessed as two adjacent 8-bit bytes, without latches (so useful only for counting pulses, or as a one-shot interval timer). A 6522 doesn't have any pin that would normally go to the RESET line, but it does have an interrupt output. If you set something in register 14 (the Interrupt Enable Register) and a timer timed out, or you created a transition on one of the handshake lines, the 6522 would generate an interrupt. The interrupts on a standard Apple ][, ][+ or //e aren't used -- it does all normal operations by polling, which is why it's so slow for some things -- and an interrupt causes the processor to jump to a location in the ROM. Just where depends on the ROM, but in an original Monitor ROM or an Autostart ROM, it ends up either going directly to the same routine as BRK does (which will perform the equivalent of a soft reset) or jumps through a vector which you're supposed to set up first. If you've not preset that, I think it ends up in the BRK routine (it certainly does in an Autostart ROM). The Er, not exactly. As Tony pointed out, the keyboard includes a decoder (called a ROM in the manual), and the key matrix is decoded by scanning. Either the X or Y lines are outputs (the manual doesn't say which, but IIRC it's the Y lines). Only SHIFT, CTRL, and SHIFT LOCK are plain inputs, and they only serve to modify the 7-bit code sent to the motherboard. I would just use the 6522. You need 12 data, plus 6 status listed above. Is there also a strobe of some sort (or is that READY?)? 8 lines on port A, plus 4 on port B for the data, CA1 for the READY or strobe, and some mixture of the remaining 4 data lines and the other three handshake lines should do it. Don't bother with interrupts to start with. Leave the IER all zeros, and just poll the IFR to look for the flag for CA1. Or just poll it looking for a negative number (which means bit 7 is set, which means one of the other flags is also set). -- Pete Peter Turnbull Network Manager University of York