14 Nov
2007
14 Nov
'07
4:17 p.m.
The LAG is labeled "HAL16R8CN 8440 /
342-0251-A" so it does look like a
custom ("HAL") chip such as what Tony was mentioning. Guess that would
It is. The important part of the number is the '16R8' bit. That implies
it's got 8 registered ouptuts and a total of 16 inputs to the AND array
(8 serpate inputs and 8 feedback terms from the output pins). That, of
course, accounts for 16 pins on the 20 pin package, the others are +5V,
ground, a common clock input to all the flip-flops, and a common output
enable signal to all the outputs).
It's the same architecture as a PAL16R8, and could be replaced by a
suitably-programemd GAL16V8. Not that that is any help at all without the
PAL equations.
I will try to find all my notes on the Mac+ (but not tonight!). I know I
never figured out the PAL equations, but I might have something of use.
-tony