1 Oct
2014
1 Oct
'14
2:54 p.m.
On 10/1/2014 1:56 PM, Tony Duell wrote:
Somethign that I forgoet to mention. The truth table,
even for a
combinatorial device, might not let you recreate the original fuse map.
The reason is that it was not uncommon to program additional terms which
apperar to be redundant, but which actually prevent glitches when the
inputs chang (if you think fo the karnaugh map, the 'extra terms' link
adjacent regions together, preventing the possible glitch when you hop
from one region to another).
Missing those out is nasty. You end up with a PAL that works on paper
(and which tests right at low speeds), but which can cause the circuit to
fail in 'intereting' ways.
That was covered in the PAL BOOKS.
Q.D = Q & Din
+ Strobe & Din
+ !Strobe & Q
-tony
Ben.