cp

Compare

Compares A with a register, memory byte or immediate value, setting flags as for subtraction without changing A.

Used in

The F registerZ80 assembly
jp, jr and the conditionsZ80 assembly
8-bit and 16-bit arithmetic, logic and bitsZ80 assembly
Arrays, strings and ixZ80 assembly
The stack, push and popZ80 assembly
Ports: in and outZ80 assembly
The screen, keyboard and mouse through portsZ80 assembly
Interrupts: im, ei, di and haltZ80 assembly
The bigger of two numbersZ80 assembly
The largest elementZ80 assembly

SZHP/VNC ●●●●1●

● set from the result
1 always 1

Forms

cp 1 byte · 4 cycles

Subtracts r from A and affects flags according to the result. A is not modified.
cp 1 byte · 7 cycles

Subtracts (HL) from A and affects flags according to the result. A is not modified.
cp 2 bytes · 7 cycles

Subtracts nn from A and affects flags according to the result. A is not modified.
cp 3 bytes · 19 cycles

Subtracts the value pointed to by IX plus dd from A and affects flags according to the result. A is not modified.

Pseudo-instructions

Other spellings the assembler accepts; each form shows the instruction it becomes.

cp a, 1 byte · 4 cycles

Subtracts r from A and affects flags according to the result. A is not modified.
cp a, 1 byte · 7 cycles

Subtracts (HL) from A and affects flags according to the result. A is not modified.
cp a, 2 bytes · 7 cycles

Subtracts nn from A and affects flags according to the result. A is not modified.
cp a, 3 bytes · 19 cycles

Subtracts the value pointed to by IX plus dd from A and affects flags according to the result. A is not modified.

Undocumented 1 row

Left out of Zilog's manual, but the Z80 runs them, and so does this emulator.

cp 2 bytes · 8 cycles

Subtracts ixh/l from A and affects flags according to the result. A is not modified.

Pseudo-instructions · Undocumented 1 row

Other spellings the assembler accepts; each form shows the instruction it becomes. Left out of Zilog's manual, but the Z80 runs them, and so does this emulator.

cp a, 2 bytes · 8 cycles

Subtracts ixh/l from A and affects flags according to the result. A is not modified.

Operands

r: An 8-bit register: a, b, c, d, e, h or l.
(hl): The byte in memory at the address stored in hl. More
nn: An 8-bit immediate value, 0 to 255 or -128 to 127, written as a number, character constant or symbol. More
(ix+dd): The byte in memory at ix + dd, where dd is a signed displacement from -128 to 127, for example (ix+5) or (ix-3). (iy+dd) works the same way. More
ixh/l: The high or low byte of ix: ixh or ixl. For iy, use iyh or iyl. More

        .org 0x8000
        ld a, 5
        ld b, 3
        cp b
        halt1
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