LD

The LD instruction is used to put the value from one place into another place.

Syntax

 LD N,M

puts M into N.

Allowed instructions
(across: M Down: N)

If x, it means allowed. If shaded in, it means not allowed.

A B C D E H L I R IXH IXL IYH IYL BC DE HL SP IX IY (BC) (DE) (HL) (IX+N) (IY+N) N NN (NN)
A x x x x x x x x x x x x x x x x x x x x
B x x x x x x x x x x x x x x x
C x x x x x x x x x x x x x x x
D x x x x x x x x x x x x x x x
E x x x x x x x x x x x x x x x
H x x x x x x x x x x x
L x x x x x x x x x x x
I x
R x
IXH x x x x x x x x
IXL x x x x x x x x
IYH x x x x x x x x
IYL x x x x x x x x
BC x x
DE x x
HL x x
SP x x x x x
IX x x
IY x x
(BC) x
(DE) x
(HL) x x x x x x x
(IX+N) x x x x x x x
(IY+N) x x x x x x x
(NN) x x x x x x x

Effects

No flags are altered except in the cases of the I or R registers.

In those cases, C is preserved, H and N are reset, and alters Z and S. P/V is set if interrupts are enabled, reset otherwise.

Uses

Use to load numbers into operands. They can either be numbers used in the code (usually 8-bits), or labels (usually 16-bits).

ld b,$05    ;Counter

ld hl,var    ;Variable label
ld a,(var)    ;Write data to var

T-States

r denotes 8-bit register.
rr represents a two byte register pair: BC, DE, HL, SP
r, r' 4
r,X 7
r,(hl) 7
r,(ix+X) 19
r,(iy+X) 19
a, (vc) 7
a, (de) 7
a, (XX) 13
(bc),a 7
(de),a 7
(XX),a 13
a, i 9
a, r 9
i, a 9
r, a 9
a, (BC) 7
(XX), a 13
rr,XX 10
ix, XX 14
iy, XX 14
hl, (XX) 20
ix, (XX) 20
iy, (XX) 20
(XX), hl 20
(XX), rr 20
(XX), ix 20
(XX), iy 20
sp, hl 6
sp, ix 10
sp, iy 10

See also

LDD,LDDR,LDI,LDIR

Source: http://www.zilog.com/appnotes_download.php?FromPage=DirectLink&dn=UM0080&ft=User%20Manual&f=YUhSMGNEb3ZMM2QzZHk1NmFXeHZaeTVqYjIwdlpHOWpjeTk2T0RBdmRXMHdNRGd3TG5Ca1pnPT0=

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