The Sinclair QL Forum

I don't think just trying to read from that address would cause that problem - as the data is in ROM.

Looking at your mods around IC2 the 74LS138 - this would replace the A15 with the A16 address line, leaving A15 to be used for pin1 on the ROMs. This put's your BASIC ROM at 0x80000 by my calculations I was planning on trying this at 0xB0000 - as that address is free in the decoding map - be interes...

I'm planning on making a similar mod - but replacing both logic chips on the right hand (processor) side of the PCB, and doing the same trick - three x 64K blocks - and the remaining socket switchable for either 128K ROM or RAM at the address designated for RAM expansion - for RAM to work - the code...

The other PCML disk interface had a 64180 CPU and ran CPM - so it may be a CPM format or derivative?

I pulled the lid off a ROM module, and pin 27 is just tied to ground. The resistor - value 2.7K goes from +5v to pin 1 of the Eprom, and the capacitor is tied between 0v and +5v. I think the same tying to ground would work perfectly well for the disk interface. I think the ICL OPD only decodes the /...

So I was looking at the circuit with a view to simplifying it. I am uncertain as to the purpose of the 74LS74 flip flops in the circuit - in the ROM modules, pin 27 is just simply grounded to indicate the presence of a device in the ROM slot - surely that could also be used here - saving a whole chi...

Derek_Stewart wrote: ↑Thu Jan 25, 2024 4:00 pm Hi,

Do not need a mouse interface, this is supplied on QIMSI.

Initially, I want some working Minerva MkII boards.

to be fair so is QL-SD equivalent provided by QIMSI

The original board was a little larger than the ROM socket footprint - having the RTC chip and GAL to accommodate. A straight copy would at least resurrect the I2C portion of Minerva. If the components were SMD - they should all fit into the same space, with the option of additional ROM images / I2C...

The main reason would be to isolate the I2C SCL and SDA pins if these are taken out to the outside world - giving protection against mishaps.

Is this to include the I2C components (clock and I2C output) ? If so could I suggest an I2C buffer chip be added ?