Any one using the 89c2051 in a battery or low power application should review:

http://www.atmel.com/atmel/acrobat/doc2213.pdf

This doc explains why you circuit isn't working. The work around cited doesn't consistantly fix the problem.

Hardware engineers are familiar with "coder's" who are sure the platform must be broken because their code "crashes".

This has resulted in a reluctance on my part to blame chips for detected fault. I always assume my configuration, parts choice or production technique need be investigated prior to blaming a chip that is presented with signals and an environment correct by data book req's.

2051 circuits are awfully simple so you can exhaust the implementation investigation quickly. So in despair i check the WEB.

regards,
p