From: William Levak (wlevak_at_cyberspace.org)
Date: 2003-01-26 04:25:08
Sounds like you have a bad data driver. I've never run into one where all
the bits had to be high in order for the write to fail, but I have had
drivers that failed when particular bits were high.
On Sat, 25 Jan 2003, Marko [iso-8859-1] Mäkelä wrote:
> Hi all,
>
> I have made some experiments with the VIC-20 cartridge prototype, which
> only has 512 kilobytes of flash ROM. I've started writing a flashing utility
> that can successfully clear the chip. (I've verified it by reading 8
> kilobytes of $ff from the chip.)
>
> However, when I program 8 kilobytes of the chip (that would be random
> locations in the chip, since I have shuffled the address lines to simplify
> the circuit board), some bytes that should be $ff are instead $fe or $fd.
>
> The embedded programming algorithm in the chip does not report any errors,
> and my program also checks that after programming a byte, it must read back
> the same within 256 retries. I also tried a modification that would skip
> any $ff bytes, but it didn't change anything. All other bytes than these
> $ff's are programmed correctly. Has anyone else had similar experience?
> Any ideas or suggestions?
>
> The next logical step is to read the whole chip (off the system) and check
> if the remaining 512-8 kilobytes of the chip are $ff, as they should. I
> hope they are, since anything else would indicate a hardware problem.
>
> Marko
>
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>
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