The instruction set provides the ability to perform bitwise XOR via <XRL A,Rn>. If, then, you have two bits on one of the MCU ports and wish to XOR them, you must isolate those bits. Presumably you know which bits they are. If you wish to operate on bits 4 and 5, then you can load ACC with the content of your port, then save the value in B. Now isolate bit 5 by ANDing ACC with 0x20 (bit 5). Then save the resulting single bit in R2. Then retrieve the saved value in B and, this time, AND with 0x10 (bit 4). Now rotate the bit left one position, and XRL ACC,R2. The result will be the XOR of the two bits. Testing for zero in ACC will give you the result.

There may, of course, be much better and more elegant ways to do this, but this is at least one way. Only a thorough understanding of the resources and instruction set of this MCU will help you to solve your problem. It might be easier to use corresponding bits on different ports, for example. Only you can decide what you need.

RE