[sdiy] Alesis Midiverb eprom images

[grant at musictechnologiesgroup.com]

Judging from the photos I think you are correct. Pin 27 is A14 and it's
pulled up to Vcc using the resistor you see. The switch probably just
grounds A14 in one position and leaves it to be pulled high to Vcc by
the resistor in the other position. This seems to indicate that the code
is 27128 size or smaller, but they just used 27256's for cost or
convenience.  So basically you have two "pages" (or banks) of 128kbits
or 32kbytes.

GB


> -------- Original Message --------
> Subject: Re: [sdiy] Alesis Midiverb eprom images
> From: Tony Kalomiris <ic1 at bell.net>
> Date: Mon, November 01, 2010 6:19 am
> To: Robin Whittle <rw at firstpr.com.au>
> Cc: synth diy <synth-diy at dropmix.xs4all.nl>
> 
> 
> Morning Robin and list memebers,
> 
> Ok I re-read your message, and think I understand now.
> The MIDIVERB and MIDIFEX units only use one half of the 27C256 eprom.
> That's why I got one half unprogammed for the first 16 K (not 256 as originally reported) - all FF's.
> Ok the programs start at $4000.
> The MVERBREV image is from the MIDIVERB and the MVERBFEX is from the MIDFEX unit, I'm guessing.
> So  I would need to load these into a 27C256 and toggle the high order address bit, not a 27C512.
> Sound about right ?
> 
> Tony Kalomiris
> 
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