The Sinclair QL Forum

After two nights' work I now have (bar the decoupling caps and pull-ups) a complete schematic of the Computer One floppy disk interface.

I found that the ROM pack pinout as posted in an earlier post needs amending. Pin 27 (marked as R/W) is "PACK_RW" (I can't remember the sense off hand) and is an output and Pin 28 (marked as PAL) is "HOST_RW", which is an input (as seen by the ROM pack).

I noticed that in the zips - one the ROM chip images is all blank. I also have a white written label in my IC7 position - which would be the "D" ROM.

I've posted it here so you can see how the contents compare:

Thanks.

Here's an version of the opd-decode.pdf with the ROM module pin-out updated from what I've learnt from the Computer One floppy interface.

First look at my Computer One floppy interface recreation...


PCB order going in to PCBWay this afternoon.

Here's the schematic:



Also: There was an error in my modified version of the decoding PDF. Pin 29 raises an interrupt.

P.S. I'm not sure if that clock circuit using the 74LS04 is going to work. *crosses fingers*

Very interested to hear if it works as I'd like one too.

Well, this is just the test version to verify my reverse engineering.

With the Mk.II I think I'll split the WD1772, clock and FDC logic onto a daughter board connected via a ribbon cable. Not only will it make the board plugging into the ROMpack smaller but it will mean that in future I can develop a board to replace the WD1772 with an emulator and SD storage, probably using a RPi Pico. The Mk.II will have some of the logic, such as the address decode, put into a GAL to reduce the chip count.

Can anyone think of a reason why the PicoVGA interface would not work with the ICL OPD ?

I just bought an early Christmas present of one of these on eBay - as the original unit I had was just the boards, and I had the keyboard from long ago. I plan on making up a small unit with a switched mode PSU and the PicoVGA board so that the device can be used with a VGA screen

You'll have to invert the RGB and sync signals from the OPD, but I think you should just be able to pass them through a 74LS04 to do that before sending them to the interface.