RE: identifying an unknown eprom content

From: Martin Hoffmann-Vetter <martinHV_at_arcor.de>
Date: Thu, 27 Aug 2020 18:45:11 +0200
Message-ID: <006c01d67c91$6ed7b1e0$6800a8c0_at_mhv.webmade.com>
Hello,

> The bytes at $e000 & $e001 are used as data, but also the irq/brk
> vector points to $e000 so any irq or brk will go into an infinite
> loop.

No, $e000 ist only used as defaut value for $0059 and $e001 as defaut value for $006a.

All hardware vectors (reset, irq and nmi) points to $e002.

> Reset or nmi will start execution at $e002.

There is a brk at $e864 that is called as error after timeout. So the reset routine is called via irq routine.

I think this is an eprom for a single mpu system with small address decoding: $0000-$3fff for ram, $4000-$7fff for io1, $8000-$bf00 for io2 and $c000-$ffff for rom. Only first four bytes are used for io1 and io2.

>> I have 2 eproms labeled: pc-central-26-4.bin (8k) and
>> boot-poste-3.bin (4) the boot-post-3.bin contains the good
>> content... [the copyright is present]
> 
> Are the two roms related? It might help to have them both

Yes, that's a very good idea. Is it possible to post the other rom, too?

Regards
Martin
Received on 2020-08-27 19:01:34

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