to help you get around the forum glitch, I start this thread


3 comments
1) P0 has no internal pullup, so it will never go high without external pullups re "the bible" which I suggest you study
2) the code you post in the blocked thread never writes to P0 (which is set to "can be pulled high" by reset.
3) the above assumes your chip is "plain vanilla"

these days posts that do not state the EXACT derivative used will often get wrong answers.

Erik

here are the links to "the bible"
Chapter 1 - 80C51 Family Architecture:
http://www.nxp.com/acrobat_d...ARCH_1.pdf
Chapter 2 - 80C51 Family Programmer's Guide and Instruction Set:
http://www.nxp.com/acrobat_d...UIDE_1.pdf
Chapter 3 - 80C51 Family Hardware Description:
http://www.nxp.com/acrobat_d...WARE_1.pdf