Jeff Otterson/N1KDO <otterson@MINDSPRING.COM> wrote:

> Maybe he can use a GAL do to his address decoding, and read-protect the
GAL.
> That method has been used by more than one vendor that I am aware of...

Protected GALs can be easy copied without reading the devices' fuse
map. It's especially easy in case of an address decoder, where no latches
are used and there is one-to-one assignment between input and output
values. I've done this several times (for replacing defective parts, not
for stealing somebody's code !). I've read the truth table of the chip with
an EPROM programmer, then reduced it and converted to a CUPL source
file using a program written in C.

- Piotr

Piotr Piatek    pisielek@inet.com.pl