Further to my question on the 74 programmer, I've read a bit more of
the new data sheet and it would appear that if the 'old' programmer
were to program the 74A version then it would be a sheer fluke.

According to the data sheet the config word has more valid bits
available. For code protection to work, bits 13 to 8 need to be set
010101  or  101010. Also the Brown out feature will be enabled or
disabled depending on how the programmer is set up as this bit was
unavailable on the 74.

In light of this it would seem I need either a new programmer or some
sort of upgrade.

Such is progress.

Thanks for the help so far

Tony


Just when I thought I knew it all,
I learned that I didn't.