Dale Wescombe <dale.wescombe@ARWNET.COM.AU> wrote:
> I can program a DIP package PIC16C73 with the same code and put it the
> same circuit and it works fine.
>
> I can use an older SO-28 PIC16C73A (batch 9731SBN) with the same code
> and put it in the same circuit and it works fine.
>
> I program a PIC from either of the two new batches and it fails to
> function at all. I have tried them in two versions of our PCBs, in a

Sounds like a classic case of an uninitialized RAM location.  The contents
are never guaranteed, but in a given batch they tend to have similar
behavior, so this kind of situation can result.

Cheers,
Eric