BOUNCE diy_efi: Admin request (fwd)

[Orin Eman]

> >From diy_efi-owner at esl.eng.ohio-state.edu  Wed Nov 11 16:18:26 1998
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> Date: Thu, 12 Nov 1998 08:11:15 +1100
> From: Richard Wakeling <kojab at ar.com.au>
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> To: diy_efi at efi332.eng.ohio-state.edu
> Subject: Help needed reading Prom.
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> Hi to you all,
> 	I have come across a 28 pin prom that I just cant get a stable checksum
> on. When I read it as a 27C128 I get FF in the bottom half of memory and
> what looks like data in the top half. With the prom in its own circuit
> pin 28 (VCC) is joined to pin 26 (A13) which would explain that they are
> only looking for data in the top section of the prom and why the bottom
> section is all FF. 
> 	The prom data lines "D0" to "D7" going to the MC68hc11 are all
> reversed, "D0 goes to "D7", D1" goes to "D6" etc. This of course will
> give the incorrect hex readings when the prom is read but what is
> causing the checksum to be different on every read attempt?
> 	I have made sure all the pins are very clean as I know from experience
> this can cause different checksums.
> 	Any help would be gladly welcome.

> Thanks in advance
> Cheers Richard.