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CHAPTER 2 CPU
2.7.4
Program Counter (PC)
The PC register is a 16-bit counter that indicates the low-order 16 bits of the memory
address of an instruction code to be executed by the CPU. The high-order eight bits of
the address are indicated by the PCB. The PC register is updated by a conditional
branch instruction, subroutine call instruction, interrupt, or reset. The PC register can
also be used as a base pointer for operand access.
■ Program Counter (PC)
Figure 2.7-10 shows the program counter.
PCB
FE H
44
Figure 2.7-10 Program Counter
PC
ABCD H
FEABCD H
Next instruction to be executed
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