Re: Blank CMS SCSI Card PCBs

["nic" <heel@ifrance.fr>]

hello
The bit security is only a way to prevent people to do a dump directly  the
content, of course if you test all the combinaisons of the pal, you would
know the fonction release by the pal or gal but it take a long time to do it
and then you have to use a coder (samll software) to create the dump.
Very often they are use to do an adress decoder in one chip instaeda of
using two or three 74ls138.
When the bit security is on you only get FFhex or 00hex value when the
burner do the dump.  it will not destroye the ship.
But of couse you have to unsolder the pal

regards
nic

ps sorry for my english...

"Rich Beaudry" <r_beaudry@hotmail.com> a �crit dans le message de news:
6fe0711e.0204260906.12acceeb@posting.google.com...
> mjmahon@aol.com (Michael J. Mahon) wrote in message
news:<20020425160322.02376.00004988@mb-fc.aol.com>...
> > Rich Beaudry asked:
> >
> > >- Would reading a PAL with the security bit set damage the PAL?
> >
> > No.  In this case "reading" means merely determining the inputs
> > and outputs and finding the truth table by applying all combinations
> > of inputs and reading all outputs.  This is a simple "behavioral" test
> > which is no more than what the PAL does in normal operation.
> >
>
> I understand what you're saying, Michael, but think of this... If it
> truly didn't hurt tht PAL, then why have the bit?  Any PROM programmer
> hardware could simply try all combinations, store the values, and burn
> another, right??
>
> I guess I've answered my own question ... Sort of ... Unless the
> security bit doesn't prevent reading, but somehow obfuscates the
> output??
>
> I guess I need to do some research, and find out what happens...
>
> Michael, you might not want to build that circuit until we can
> determine if damage will be caused...
>
> Rich B.