HP9816 PAL16L8

[Tony Duell]

On Tue, Jun 11, 2019 at 12:23 AM Paul Berger via cctalk
<cctalk at classiccmp.org> wrote:
>
>
> On 2019-06-08 7:14 a.m., Piero Andreini via cctalk wrote:
> > desperately looking for jedec file of PAL 16L8 position U69 part # 1820-2991

> We can hope that it is all combinational logic and I can run trough all
> combinations of inputs and capture the output and we can develop
> equations that way as long as they did not do anything like use feedback
> to create registers as one person suggested could be done.

You can detect sequential logic in the PAL by :

For each combination of inputs :
   Read the outputs
     Toggle an input (change from 0 to 1 and back again or vice versa)
     Compare the outputs to what they were before -- if they have
changed then there's a sequential function on that input
     Check the next input
  Check the next combination of inputs


It is my guess that the logic in this PAL is much the same as the DMA logic,
etc (but cut down to only support DMA channel 0) of the HP98624 HPIB card.
This board uses only TTL, no PAL, so you might be able to work out suitable
equations from that.

-tony