[ukvac] [Tech] Prom/Rom compatibility & capability questions
Hi guys (and welcome back to reality Andy!),
I finally got round to taking a day off work and starting to look at some of
the duff boards i have on Friday.
I have a recently aquired faulty Do Run Run board. Things were going fairly
well, i managed to fix the lines through the sprites, but along the way,
i've caused a few other problems:
Lesson number 1 NEVER assume that a replacement part is any better than the
faulty part! If i'd questioned that the ram fault didn't go away when i
piggy backed the new chip i wouldn't have caused the following.
I was tired, wasn't thinking properly and when questioning the logic chip
that takes the output from the ram, i piggy backed another on top of it. I
then caused problems with the background graphics. Thinking about it, am i
right in saying you cannot piggy back logic chips without disconnecting the
power to the bottom one?
Anyway, i carried on and started swapping things over with a known good
board. Course, plonka here accidentally (wasn't too awake) reinserted a prom
the wrong way round and rather than immediately switching things off as soon
as i heard a crackle, i had to look and see what was crackling, by which
time there was smoke and a dead prom - doh!
Now then, some questions to be answered please...
1) Is an 82S147N compatible with a N82S147N? - the latter (that is in there
at the mo) is double the price! - oh, and does anyone have any please, as i
want three (one will suffice, but three would be ideal) i don't really want
to be paying over ten quid each for them!
2) Can anyone program these? My progger doesn't do them :O(
3) Logic chips - while an LS74S374N (original part) is pin compatible with
an LS74LS374N, the specs are different. Would this fry something else
causing background corruption? The original 74S374 seems okay (remember it
turned out to be the ram chip, not the logic chip). - i have bucket loads
(well, not quite!) of the LS variety, but none of the S variety.
4) Finally, (bit more ambitious), is there anything to stop me burning the
code from the knacked prom onto a normal eprom and wiring that to the
socket? Would it matter that the eprom was much larger than the prom? Surely
the CPU just wouldn't see the empty higher address space would it?
Thanks for any help - i actually understood what was going on with this
board (which is a first!), but managed to do a few stoopid things anyway!
Cheers,
Martin.
---------------------------------------------------
Martin White
Coming real soon...
http://www.guddler.btinternet.co.uk
Yet another arcade site(!) with info on games owned, repair logs (as and
when), projects and more.
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
Hi guys (and welcome back to reality Andy!),
I finally got round to taking a day off work and starting to look at some of
the duff boards i have on Friday.
I have a recently aquired faulty Do Run Run board. Things were going fairly
well, i managed to fix the lines through the sprites, but along the way,
i've caused a few other problems:
Lesson number 1 NEVER assume that a replacement part is any better than the
faulty part! If i'd questioned that the ram fault didn't go away when i
piggy backed the new chip i wouldn't have caused the following.
I was tired, wasn't thinking properly and when questioning the logic chip
that takes the output from the ram, i piggy backed another on top of it. I
then caused problems with the background graphics. Thinking about it, am i
right in saying you cannot piggy back logic chips without disconnecting the
power to the bottom one?
Anyway, i carried on and started swapping things over with a known good
board. Course, plonka here accidentally (wasn't too awake) reinserted a prom
the wrong way round and rather than immediately switching things off as soon
as i heard a crackle, i had to look and see what was crackling, by which
time there was smoke and a dead prom - doh!
Now then, some questions to be answered please...
1) Is an 82S147N compatible with a N82S147N? - the latter (that is in there
at the mo) is double the price! - oh, and does anyone have any please, as i
want three (one will suffice, but three would be ideal) i don't really want
to be paying over ten quid each for them!
2) Can anyone program these? My progger doesn't do them :O(
3) Logic chips - while an LS74S374N (original part) is pin compatible with
an LS74LS374N, the specs are different. Would this fry something else
causing background corruption? The original 74S374 seems okay (remember it
turned out to be the ram chip, not the logic chip). - i have bucket loads
(well, not quite!) of the LS variety, but none of the S variety.
4) Finally, (bit more ambitious), is there anything to stop me burning the
code from the knacked prom onto a normal eprom and wiring that to the
socket? Would it matter that the eprom was much larger than the prom? Surely
the CPU just wouldn't see the empty higher address space would it?
Thanks for any help - i actually understood what was going on with this
board (which is a first!), but managed to do a few stoopid things anyway!
Cheers,
Martin.
---------------------------------------------------
Martin White
Coming real soon...
http://www.guddler.btinternet.co.uk
Yet another arcade site(!) with info on games owned, repair logs (as and
when), projects and more.
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
