PROM Size on a 165

[ae2598 at wayne.edu]

Is double-loading the thing to do, instead of just blanking out the second
half?  I ran into the same situation at work, I took an image off a 128 to
replicate, but only had 256's to use for the copies.  Nobody around here
had 'em in stock, either.. 128 must've been an unpopular size?  Anyway I
took the 128 image, only write the first 1/2 of the chip, leaving the high
side blank, and it seemed to work.  I guess the success of this would
depend on what the 128 circuit does with the pin that is used as the
high-order address line on the 256, I can't remember if it was NC or if it
had some other use on the 128.

 On Thu, 16 Nov 2000, Bruce Plecan wrote:

> 
> Double load the 128 image in the 256 and be done with it (er go for it)
> Bruce
> 
> 
> 
> > Newbie working on a 165 ECM.  I have many 256 PROM's but no 128's.  I'd
> like
> > to put the 256's to work.  The schematic's I have seen on ECMGUY's site,
> > show what looks like PROM pin 27 wired to A14 of the ECM bus.  (CS and OE
> > are also reversed)  This does not make sense.  Pin 27 of the original 128
> > PROM is /pgm pin, which should be tied high in the ECM.
> >
> > I'm guessing the schematic was made from a later version ECM that takes
> 256
> > PROM's.  (Hense the A14 connection.)
> >
> > Does the MEMCAL not interface w/ A14 on the ECM board?  i.e. Does the
> MEMCAL
> > tie PROM pin 27 high?  Can someone confirm that PROM pin 27 on a 165 ECM
> is
> > held high all the time?  Will using a 256 part for a 128 ECM cause error
> > conditions for certain BIN editors?  i.e. Do the editors check this?
> >
> > I apologies if this has been discussed before, I have not yet found the
> > archive seach.
> >
> > ML
> >
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