With the collective Brain Trust on this board,
it wouldn't surprise me if someone hadn't at least tried this...

I'm trying to copy a PAL16L8 which has the security bit set.

I'm told that I can use "brute force" to trigger each possible input combination (2^11)
and then read each output.

From there, I need to reverse-engineer the truth-tables...

Anyone tried this ?
....Bueller ?  ....Anyone ?

thanks,
Steph

Quoted from Steph

I'm told that I can use "brute force" to trigger each possible input combination (2^11)
and then read each output.
From there, I need to reverse-engineer the truth-tables...

That's one way of doing it .... but it's also the hardest way, depending on whether or not the design uses latched outputs or not (ie: does the design use a clock pin as an input).

The easiest way, is to study the schematic, and try to fully understand what the PLD does in the cct.
What inputs does it use to achieve what outputs that the cct requires, to perform it's function.
16L8 designs are very primitive by today's standards .. they were usually implemented to simply replace 2 or more TTL family gates or registers. Of course by 'locking' in the design, they add a bit of security to the design, albiet very little.

Step 1: Understand what the device needs to do.
Step 2: Draw out a similar design of the PLD in standard gated logic.
Step 3: Write out your new gated logic design in Boolean algebra equations... an EQN file.
(ie: input A AND input B = output C, etc, etc.)
Step 4: Download an old free version of National Semiconductor's OPAL, and compile your design to a target  reprogrammable PLD like a GAL16V8.
Step 5: Program your GAL IC & test your theory in a real board.
-repeat steps 2 - 5 until you have a working replacement.

Good Luck!

[ I figured if anyone would reply, ... it would be ToMmy !     ]

Thanks for the info.

I've got the schems and know that inputs are pins 1-9 & 11,  [standard 16L8 pinout]
and outputs are 12, 14,15, 17, 18, & 19  (pins 10 and 20 are VCC and Gnd)

I'm thinking of making a socket adapter with a 2716 pinout,
and then try to read it as such.

The Data read should only be 6-bit wide so it shouldn't be to difficult to figure out the truth-tables....

I'll let you know how it works out.

Cheers,
Steph

woozle wozle?