Bit Operations - Nintendo GAME BOY Programming Manual

Game Boy Programming Manual

2.6 Bit Operations

BIT b,
Copies the complement of the contents of the specified bit in register r to the Z flag of the program status
word (PSW).
The codes for b and r are as follows.
Bit
0
1
2
3
4
5
6
7
Examples: When A = 80h and L = EFh
BIT 7, A ; Z ← 0, H ← 1, N ← 0
BIT 4, L ; Z ← 1, H ← 1, N ← 0
BIT b,
Copies the complement of the contents of the specified bit in memory specified by the contents of
register pair HL to the Z flag of the program status word (PSW).
Examples: When (HL) = FEh,
BIT 0, (HL) ; Z ← 1, H ← 1, N ← 0
BIT 1, (HL) ; Z ← 0, H ← 1, N ← 0
Z ←
r
rb
b
000
001
010
011
100
101
110
111
Z ← (HL)
(HL)
b
CY H
--
1
Register r
A 111
B 000
C 001
D 010
E 011
H 100
L 101
CY H
-- 1
114
N Z CYCL 7 6
0 2 11
rb
01
N Z CYCL 7 6 5 4 3
0 ( ) 3 11
HL
b
01
5 4 3 2 1 0
001 011
b r
2 1 0
001 011
b 110