25 Apr
2009
25 Apr
'09
11:30 a.m.
It's even more frustrating when you're looking
at some CPLD or PAL
that's gone south. You don't have the original part to reverse-
engineer, the manufacturer is unlikely to furnish a replacement or
even the programming for the part. Usually, this means that your
widget is junk.
This is why I try to make backups of programmed parts while the device is
still working. Of course some manufactures plow the protection fuse, so
you can't easily read the device out (although for PALs, I believe it's
always possible to deduce the logic equations with a bit of work without
having to dump out the fuse map, there is no hidden internal state). A
suprising number of classic computers, though, have unprotected PALs, etc.
-tony