Re: VIC-20 IF BOARD

From: Gerrit Heitsch <gerrit_at_laosinh.s.bawue.de>
Date: Sat, 26 Apr 2014 17:55:47 +0200
Message-ID: <535BD703.5060003@laosinh.s.bawue.de>
On 04/26/2014 05:43 PM, Ruud@Baltissen.org wrote:
> Hallo smf,
>
>
>> Can you dump and upload the rom somewhere?
>
> I tried to read the EPROM but I think it is brooken. Every time
> after a read my burner reported verify errors. And worse, the first
> 30 bytes are zero. It has a Z80 on board so the certainly the first
> few bytes must contain something.

Not necessarily.. If I remember right, the Z80 just starts executing 
Code at $0000 after a Reset. And the Opcode for NOP is $00. So it would 
just start up, execute 30 NOPs and then do whatever the rest of the code 
demands.

It wouldn't make much sense, but it could be possible.

An EPROM that loses its contents due to age reverts back to $FF for that 
cell.

  Gerrit





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