Amiga not booting ( was 27C400 EPROM emulators (beta) issue D technical discussion)

[cmorley]

OK great, USB working. All modules were programmed with Chucky's Diagrom (A500) after test. Try programming the appropriate diagrom for your machine. Try both byte swaps if unsure. You can find out which ROM slot is selected over USB from the info command.

[nivrig]

I wouldn't directly suspect the caps on the motherboard but if there are a few things wrong...
What is the 5V at the CPU?

Solid 5.04v, measured on the accelerator card.

[amimjf]

OK great, USB working. All modules were programmed with Chucky's Diagrom (A500) after test. Try programming the appropriate diagrom for your machine. Try both byte swaps if unsure. You can find out which ROM slot is selected over USB from the info command.

Alas still issue with purple screen on power on (in my rev 6.2 A2000). But was able to program the KS3.2.1 *.bin file (for physical chips, not the swapped *.rom ones for emulators), so the ST micro is fine.

As you say you ship with diagrom, but that purple screened as well. Real physical 27C400 KS3.1 works fine.

Will do some reading on A2000 purple screens, but it looks like no code is running from the ROM, not floppy clicks, nothing.

[amimjf]

Tried burning both rom/bin files with and without byte swap, no joy.
Reseated socket several times.
LED does not light up, but not sure under which conditions it should ?

Versions are; is an update available ?
STM32 firmware 0.8 (C)2020 Chris Morley
CPLD firmware 0.10 (C)2020 Chris Morley

Nothing conclusive on purple boot, its not an official colour.

[cmorley]

Sorry, I don't know what LED you are talking about.

If you send it back I can test it.

[amimjf]

Hi,

The "enable LED" option on the EPROM emulator,.. sorry i thought it might have been an indication LED.

Will play a bit more, p.s now i can program images its pretty cool to use, just like the JTAG devices we use at work.

[cmorley]

The "enable LED" option on the EPROM emulator,.. sorry i thought it might have been an indication LED.

Will play a bit more, p.s now i can program images its pretty cool to use, just like the JTAG devices we use at work.

oh. you can connect an LED to one of the pads. e.g. to power LED on a C64. I don't think anyone uses this function - especially not on Amiga.

If you have been adjusting options rerun the setup wizard for 27C400 which will reset all the defaults for pull ups etc.

[nivrig]

lukzer has tested the emulator I sent him on a Rev6a A500 with a HC533 fitted and it worked perfectly. He's going to send me a new HC533 firmware file, but it's expected to be the same as the version I already have.

I have now tested two versions of HC533 firmware, with no improvement.
Both work fine with a ROM chip but crash as before with the emulator in place.

[cmorley]

Both work fine with a ROM chip but crash as before with the emulator in place.

Sorry without seeing your Amiga motherboard on a bench with test equipment I can't really help. My guess would be that you have a problem with noise or ground bounce on your board and the EPROM emu responds (and crashes the bus) where a real EPROM can't respond in time. You could try a different Gary (which creates /ROMEN signal IIRC) if you have a spare.

[nivrig]

Yeah, no worries. It's a puzzler. I'll maybe try to get a signal trace off /ROMEN and see what it looks like.