[Coco] rom help needed II

Joel Ewy jcewy at swbell.net
Tue Nov 27 10:56:55 EST 2007

Mike Kandrac wrote:
> I am in need of some help. I was fixing a few extra coco boards I had and was trying to make copies of the ecb chip but Im not able to copy the ECB of the color basic 1.0 or 1.2 chip my programmer seems to be able to read them as 27XXX chips but when I burn them to EPROM all I get is garbage. can anyone help me out as to tell me what im doing wrong ? 
> I am trying to copy the original  Rom  which is a 24 pin color basic 1.2  to the MCM 68766.
> the problem seem to be the original Rom which my programmer reads as a  generic 27XXX  when I open the editor I can see color basic 1.2 about 12 lines down 
> when I try to copy it to the 68766 it looks the same but wont run 
What kind of EPROM programmer are you using?  Is there a way to force it
to the 68766 part type?  I have an old MCT thing, and in the DOS
software that runs it, I can select the part type.  I believe some of
the address lines are different between the 68766 and the 27xx --
probably just the high bit.  So the first part of the data may appear
correct, but the upper memory locations may not be read at all.  That
would probably be the upper 4K of an 8K chip.  I think the 27xx-series
chips end at 4K in the 24-pin package.

> sincerely
>  Mike 
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