30 Jun
2005
30 Jun
'05
10:06 a.m.
If you have the original 40 column board, can you take a look inside and
see if the 5th IC in from the right on the top row of chips (first one
in after the DRAM) is a 74LS158?
All the schematics show this as being a 74LS157 but it's got an LS158 on
my board (which IIRC inverts the outputs).
If the schematics are wrong I'll scribble a note on the copies that I
have!
(I'm trying to trace a fault on my board which is resulting in corrupted
screen memory, and having the schematics disagree with the actual board
is annoying! :-)
cheers
Jules
30 Jun
30 Jun
12:44 p.m.
If you have the original 40 column board, can you take a look inside and
see if the 5th IC in from the right on the top row of chips (first one
in after the DRAM) is a 74LS158?
All the schematics show this as being a 74LS157 but it's got an LS158 on
my board (which IIRC inverts the outputs).
My 380Z is hell to get to at the moment (there's a Philips 5200 word
processor and then some bits of HP 98780A monitor chassis on top of
it...). But I've looked at the schematics and the only muxes I can see
are for the DRAM address. Can you confirm that this chip is one of those.
If it is, then I think it doesn't matter if the output is inverted or not.
The address lines to the RAM will be inverted for both reading and
writing, so there'll be no problem.
-tony
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