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27C400/27C800 EPROM emulator

Posted: Sun Jul 14, 2019 6:41 pm
by cmorley
Hi,

Not sure which forum to put this in so general hardware it is.

First prototype for my new USB programmable EPROM emulator. Supports the _BYTE pin so 8/16 bit compatible. Does ROM switching via a 'reset' line or driven from switches/logic by way of the top side spare pads. So 4x 27C400 or 2x 27C800 images.

So not exclusively an Amiga kickswitcher (does support the Commodore A17 pinout & JEDEC EPROM pinout) and could be used in any retro gear that takes a 16 bit ROM or an 8-bit ROM by way of a mezzanine board to jig the pinout. So it should work in all manner of stuff... drum machines, synths, computers etc.

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I'll be looking for some power user beta testers in a few weeks time covering a bunch of different hardware if possible.

Chris

Re: 27C400/27C800 EPROM emulator

Posted: Sun Jul 14, 2019 9:11 pm
by exxos
Pretty cool looking bit of kit! :thumbup:

Re: 27C400/27C800 EPROM emulator

Posted: Mon Jul 15, 2019 8:02 am
by terriblefire
Would love to test this out! Can it be wiped/reprogrammed by a TL866?

Re: 27C400/27C800 EPROM emulator

Posted: Mon Jul 15, 2019 8:11 am
by chucky
USB programmed? so I could program it while still on the board? this would help me alot when developing DiagROM and I need to test on a real machine.. *starts thowing money on monitor*

Re: 27C400/27C800 EPROM emulator

Posted: Mon Jul 15, 2019 9:30 am
by cmorley
terriblefire wrote:
Mon Jul 15, 2019 8:02 am
Can it be wiped/reprogrammed by a TL866?
No, only USB program via a virtual comm port - just fire a BIN file over serial. I don't think the 74LVC buffer on A9 or _BYTE/Vpp would survive the ID read/Vpp voltage :shock: (I was going to add a warning "do not insert in a EPROM programmer" rather than add protection on those pins)
chucky wrote:
Mon Jul 15, 2019 8:11 am
USB programmed? so I could program it while still on the board? this would help me alot when developing DiagROM and I need to test on a real machine.. *starts thowing money on monitor*
Yes fully in circuit programmable. The data bus goes high-Z when you program so maybe turn the Amiga power off though!

Re: 27C400/27C800 EPROM emulator

Posted: Mon Jul 15, 2019 11:05 am
by Cyprian
cool project,
does it fit to ST?

Re: 27C400/27C800 EPROM emulator

Posted: Mon Jul 15, 2019 11:42 am
by terriblefire
If its USB programmed its perfect for me. No more unplugging.

Re: 27C400/27C800 EPROM emulator

Posted: Mon Jul 15, 2019 12:57 pm
by cmorley
Cyprian wrote:
Mon Jul 15, 2019 11:05 am
cool project,
does it fit to ST?
I understand the ST ROMs are 8-bit viewtopic.php?f=16&t=607. So an adapter would be required to match the correct pinout - simple enough PCB project.

Re: 27C400/27C800 EPROM emulator

Posted: Mon Jul 15, 2019 1:39 pm
by tzok
What is the access time?

Re: 27C400/27C800 EPROM emulator

Posted: Mon Jul 15, 2019 2:01 pm
by cmorley
I have 70ns and 55ns FLASH to test with. We lose a little margin with the buffers but gain some because the chips are faster than their datasheet say.

Worst case 80ns (70ns FLASH). Very much faster than most retro computers would need.