LDD

LDD

Load and Decrement

Description

Copies one byte from (HL) to (DE), then decrements HL, DE, and BC.

ld (de),(hl) ; Not normally a valid instruction
dec hl
dec de
dec bc

Uses

• This instruction is not very useful on its own, but more often used is the repeating version of LDD: LDDR

Results

Register/Flag	16-bit (non-ADL)	24-bit (ADL)
S flag	Not affected
Z flag	Not affected
H flag	Reset
P/V flag	Set if BC ≠ 0 after the operation; else reset
N flag	Reset
C flag	Not affected

Allowed Instructions

Instruction	Opcode	CC (ADL/non-ADL)	CC (.S)	CC (.L)
ldi	$ED, $A8	2F + 1R + 1W + 1	3F + 1R + 1W + 1	3F + 1R + 1W + 1

Notes

• If all you want to accomplish is ld (de),(hl), consider ld a,(hl) \ ld (de),a. It is the same size but is one clock cycle less and doesn’t modify any of the registers except A.

See Also

CPD, LD, LDI, LDDR, LDIR