Hi Declan, if the security fuse of the PALs/GALs/PALCEs was activated then there is no chance for you to ever read out the checksum of your devices. Normally a manufacturer would protect his logic design by activating the security fuse....
Uwe. > Recently, Somebody Somewhere wrote these words >> I suggest you quit messing around with check sums and get to work. ;-) > Unfortunately, that's a no can do. I need the checksum of that PAL > to ever get a replacement from these guys in the future. This is > to fix a 1999 version of a machine sold from 1992 - 1999. Those > guys are 2 model revisions on. >> Who was it that offered the defination of insanity as repeating the >> same experiement and expecting different results? >> Your boolean equations, and therefore your check sums, must be right >> or couldn't get it to boot with one of the old PALs. Ordinarly PAL >> programmers automaticly checksum so if there was a problem I think the >> programmer would say so. > Maybe my explanation lacked. One of my PALs has a pin blown (Pin > 23) The manufacturers won't replace the one, they feel I should replace > the four. They can't supply me correct PALs. Here's where the > checksums of mine become relevant. They haven't a clue really, and > I have the only working part for one of them. >> Your symtoms suggest you are running ripple logic with faster PALs. >> If so, you are trying to fix a bad design rather than a simple >> compoent failure. In short a hard road to hoe. > I Agree totally - fixing a bad design is what I am trying to do. > They do have 74BCT (Texas bus logic) all over the place. >> Here is where I'd start. >> 1. Check your power supply. Make sure it is absolutly clean. Faster >> devices are more sucesptable to noise. Add bypass caps if you >> don't see them on the PALS. Check out the power supply >> electrolytics. > The power supply isn't perfect, but it's reasonably good. I'll add > bypass. But this fault developed with heat (Cold everything worked > - warm it failed) and then became permanent. I am not thinking of > power supply issues, even thou that has had a ressurection. >> 2. See if you can find low power equivalents for your PALs. Quarter >> power versions are ideal. That does not mean switch to CMOS. The >> idea of using low power bipolar versions is they are much slower >> devices. It's not to save power. Remember speed kills. >> > I can't choose the PALs they program! They won't give me the code. > My guess is they are programming in the wrong files. I have reason > to believe this (They hunted for weeks and then came up with these). > So I'm about proving they have the wrong parts and pointing them > at the right ones. > -- > With best Regards, > Declan Moriarty. -- Author: Uwe Zimmermann INET: [EMAIL PROTECTED] Fat City Hosting, San Diego, California -- http://www.fatcity.com --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
