Search found 429 matches

by stephen_usher
Thu Jan 25, 2024 9:27 pm
Forum: Compatibles Corner
Topic: OPD: Computer One floppy interface recreation.
Replies: 26
Views: 19065

Re: OPD: Computer One floppy interface recreation.

The 74LS74 is really not needed. Normal ROMs probably only pull the line low when /CE and /OE are send from the host interface. What the circuit in the interface is doing is effectively pulsing the line high every clock cycle for a few nanoseconds, which makes zero sense.
by stephen_usher
Tue Jan 23, 2024 10:28 pm
Forum: Compatibles Corner
Topic: ICL OPD
Replies: 180
Views: 166846

Re: ICL OPD

I'm glad you finally got things working. Note that copying to Goteks running FashFloppy has an issue where the copy fails saying that the destination drive is missing or unusable after it's taken an age changing the FAT setting up the copy and then starting to copy. Saving from applications etc. wor...
by stephen_usher
Tue Jan 23, 2024 1:56 pm
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

Yay!

The ROM versions are a set so you can't mix and match. Mine are:

XBAA03
XBAB04
XBAC03
XBAD03

The XB series means mask ROMs. The Q???? versions are the EPROMs containing the same data.
by stephen_usher
Tue Jan 23, 2024 9:16 am
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

The ZX8301 does seem to be liable to failure. My OPD has had it replaced "in antiquity".
by stephen_usher
Mon Jan 22, 2024 10:25 pm
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

I thought that he meant the other one. Anyway, SRAM error is 5 stripes.
by stephen_usher
Mon Jan 22, 2024 9:52 pm
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

By the way, if the second /CE stays high then whatever is supposed to bring it low so that the CPU can read it isn't doing its job. Time to trace that back on the board to find where it goes.
by stephen_usher
Mon Jan 22, 2024 8:36 pm
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

If the ROMs were bad you'd get four stripes as they'd fail their CRC checks.

I wonder if a capacitor has gone bad and you're getting noise on the power rail. Something's very screwy.
by stephen_usher
Sun Jan 21, 2024 7:11 pm
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

SRAM issue I found on my machine was the lack of the POWER-GOOD from the power supply, listed as "shutdown" on the pinout.

Check VCC (from the 3V battery) and /CE (from PSU via MOSFET on the left of the board) on the SRAM chip.
by stephen_usher
Sun Jan 21, 2024 2:46 pm
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

If the ROMs were damaged then you'd get 4 lines as this is when they fail their CRC check. If it's getting to the Iinitialising page then it's actually booting "fully" before resetting. i.e. it's passing the power on tests, including memory test (but this is rudamentary at best). I would r...
by stephen_usher
Sat Jan 20, 2024 11:50 pm
Forum: Compatibles Corner
Topic: ICL OPD 3 vertical white stripes fault
Replies: 24
Views: 1244

Re: ICL OPD 3 vertical white stripes fault

You need the ROM pack and the telephony module to fully boot, it will hang at a blank screen otherwise. It doesn't matter about the 9V battery, that merely keeps the real-time clock going. The 3V battery keeps the "Permanent Store" SRAM energised. It isn't required to be OK. If the content...