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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Important Questions from Instruction Set of 8085
Calculate the time required to execute the entire instruction cycle if two machine codes, 0011 1110 and 0011 0010, are stored in memory locations 2000H and 2001H, respectively.
If the clock frequency is 2 MHz, the first machine code represents opcode to load data byte in the accumulator and the second code represents data to be loaded in the accumulator.
Following instruction is executed in 8085, LDB 4000H
Identify the correct statement.
In 8085A microprocessor, the operation performed by the instruction LHLD 2100H is
__________ address instruction is supplied to the microprocessor by an external device for INTR signal acknowledgement.
A fetch cycle is the
