Actually, there should be a difference between MOV Rn,ACC and MOV Rn,A in the hex output. Assuming you are working with R0, the first option would produce the opcodes "A8 E0" wheras the second option would produce the opcode "F8".

Both instructions will accomplish the same thing functionally, but the second option takes 1 byte of code memory instead of two and takes one instruction cycle instead of two cycles. So it requires half as much memory and is twice as fast.

Craig Steiner