How exactly do PAL chips get programmed?

[Jules Richardson]

Tony Duell wrote:
> If you know the device type and manufactuer and have a programmer that 
> supposts that _exactly_, it won't hurt to try to read it out.

Presumably there are all sorts of 'standard' formats for storing read-out PAL 
information, so:

1) What's the most sensible format to use, and

2) Is it possible for a PAL to fail reading in such a way that the data you 
get out is junk - but not *obviously* junk to the user? (if I go around 
backing PALs up I'd like to know for sure that the backups are good - but 
obviously testing them at backup time by writing a new device for every single 
one isn't much of a solution! :)

cheers

Jules