Re: Blank CMS SCSI Card PCBs

[david@uow.edu.au (David Wilson)]

r_beaudry@hotmail.com (Rich Beaudry) writes:
>Let me preface this by saying that I am a *total* newbie to
>programmable logic, but the way I understood PALs is that you don't
>necessarily know what is an output, and what is an input.  You may
>know that there's a max of, for example, 8 inputs, but you don't know
>where (what pins) they are....  It may not be impossible to decipher,
>but I didn't think it was that easy ... Otherwise, why have a security
>bit??

Ok, I have worked out which pins are inputs and which are outputs.
I did this by pulling the chips, inserting then into a `breadboad'
and powering each one up in turn. I then used a logic probe to determine
which pins were floating (inputs) and which were driven (outputs).

U14 A1	inputs 1-9,11		outputs	12-19
U16 A2	inputs 1-9,11,17	outputs 12-16,18,19
U9 A3	inputs 1-9,11,13-16	outputs 12,17-19

So, provided none of the pins are bi-directional all I have to do is step
through the 2^10 (2^11 and 2^15 respectively) possible inputs and record
the outputs. Then I look for patterns and derive the equations.
--
David Wilson  School of IT & CS, Uni of Wollongong, Australia