Peter,

I looked at your previous posts on this topic. Can you explain how to read the P2 latch when executing from internal code space?

>>on using external code execution, you can >>never read back P2.
>>Please use a function, executed from the >>internal code space,
>>to read back P2.


>>If no internal code space available:

>>1. everytime, if you modify P2, store the >>same value
>>to a byte in the internal RAM (= shadow >>register).

I don't understand how using the DPTR is going to help reading the P2 latch. Please explain.

>>2. use DPTR instead of P2

Surely the JBC instruction in the following method will change the P2 latch contents?

>>3. you can read back P2 bitwise with using
>>the JBC instruction (see 8051 manual for >>details):

>>mov a, #0FFh
>>jbc P2.0, tb0
>>clr acc.0
>>tb0: jbc P2.1, tb1
>>...
>>tb6: jbc P2.7, tb7
>>clr acc.7
>>tb7:

Thanks