The Sinclair QL Forum

It will depend a bit on which IPC you are using. It would mean counting the states / cycles for the instructions between setting the row address and then reading the column data in.

In the original IPC code:

; scan keyboard, entry A (one bit=1), ret A
05C8: 39 OUTL P1,A output A on P1
05C9: AB MOV ...

It would have been interesting to see how many QL's had to be repaired because of 'dodgy' chips, and compare with the cost of socketing some of the more common chip failure areas - in other words - was it worth the cost saving ;)

I can see why the ROM's were socketed - but even there - Sinclair ...

It's not so much VPA generating VMA, but VPA signal being used for more than one purpose. You need to look at the state of the 3 Function code lines FC0-FC2, although the QL pulls a trick there and only uses 2 of these (FC1 and FC0) to generate the VPA signal using a NAND gate.

So whenever there is ...

The fact the 8049 can control both interrupt lines seems to be a hangover from the development days - interrupt level 7 (NMI) is basically set by pressing CTRL ALT 7 on the QL keyboard - this triggers code in the 8049 for it to reset itself and at the same time trigger the NMI on the QL - the usual ...

I remember seeing output like that with Aurora card and qubide where my qubide card had a bridge between 2 address lines, causing a short on the bus. The regular repeating black lines are a giveaway. I would check the adjacent address lines and see if you have a solder bridge somewhere, could be a ...

That is impressive!

X axis looks ok for a 7.5MHz, given that signal is repeating roughly 2/3 of the scale interval

In the message in the Wanted Section:



As for the ULA, I don't know if anyone has reverse engineered that one. It's probably quite simple.


As part of my Service Manual update, I was looking at the Microdrive, giving a more detailed description of the Microdrive circuitry Headboard and ...

The service manual mod list is here:

https://www.sinclairql.net/srv/qlsm4.html#s4c

I replaced that keyboard connector on a couple of QL's with a JST connector - it just makes life easier if you have to get inside the machne...

That's good news - looking forward to seeing this!