In the 8085 microprocessor, what does the instruction PCHL do?
Loads the PC with HL
The PCHL instruction of the 8085 microprocessor performs the register-transfer operation:
PC ← HL — that is, it loads the Program Counter with the contents of the HL register pair.
Because the Program Counter holds the address of the next instruction to be fetched, overwriting it with the 16-bit value in HL forces execution to jump to that address. Key points:
- It behaves as an unconditional register-indirect jump: the high byte H goes to the upper half of the PC and the low byte L to the lower half.
- It is a compact 1-byte instruction requiring no operand, and it does not affect any status flags.
- Because the destination address is computed at run-time in HL, PCHL is ideal for jump tables, computed GOTOs, and returning to a dynamically calculated address.
The reverse operation — loading HL with the PC — is not what PCHL does; the mnemonic order (PC then HL) reflects the destination-then-source direction PC ← HL. Popping the PC from the stack is the job of RET (and conditional returns), while pushing the PC onto the stack is done by CALL instructions; PCHL involves the stack in no way at all.
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