I'm using MX 27c1000dc-12 is this eprom mask compatable?
The original chip was -20 is the faster chip an issue?
Two things....
For whatever reason, MX uses the number "27c1000"
for their JEDEC version. (ie. it is the same as a "normal" 27c1001 ).
This is hugely confusing, and had me guessing when I first used those chips.
So MX 27c1000 = "standard" 27c1001 = JEDEC
This is NOT the same as the NEC 27c1000,
which is a true mask-eprom.
So set your programmer to NEC 27c1000 or Hitachi 27c301.
Both of these WILL read correctly.
(...and probably program too... )
NB. Not all programmers support mask-roms,
so if you can't find the two types I listed above (...which are the most common),
your programmer can probably not support them.
--
As for speed, the SMALLER the number, the FASTER the eprom.
-12 means 120 nsec, -20 means 200 nsec
This is READ-ACCESS speed.
So the smaller the number, the FASTER the eprom reads the data
(ie. it is FASTER).
So -12 is FASTER than -20 ( ...I know, it's confusing ! )
For programming or using a programmer, speed makes no difference whatsoever.
( A programmer will read or program eproms of ANY speed ).
Where speed becomes an issues is on PCB where the clock cycle
is faster than the read-access of the eprom.
If you have a fast clock ( say 150 nsec pulse ),
-20 eproms won't work ( 200 nsec too slow for 150ns pulse ),
but a -12 eprom will work ( 120 nsec is fast enough to provide data within the clock pulse)
Truth be told I've rarely seen instances where an eprom was too slow,
but it can happen.
For any eproms over 1Mb (27c010 and up), you're "probably" OK with -20,
fine with -15, and laughing with -12.
Clear as mud ?
;-)
Steph