hsabaghianb @ kashanu.ac.ir Microprocessors 1-56
The R register
Is increased at every first machine cycle (M1).
Bit 7 of it is never changed by this; only the lower 7 bits are included in the addition. So bit 7 stays the same
Bit 7 can be changed using the LD R,A instruction.
LD A,R and LD R,A access the R register after it is increased
R is often used in programs for a random value, which is good but of course not truly random.
the block instructions decrease the PC with two, so the instructions are re-executed.