BIT

BIT b,M

Test Bit

Description

Checks the b``th bit of ``M and stores the inverse in the Z flag. b must be a hard-coded number between 0 and 7.

Results

Register/Flag	8-bit	16-bit (non-ADL)	24-bit (ADL)
S flag	Undefined
Z flag	Set if bit b of M is zero
H flag	Set
P/V flag	Undefined
N flag	Reset
C flag	Not affected

Allowed Instructions

Instruction	Opcode	CC (ADL/non-ADL)	CC (.S)	CC (.L)
bit 0,a	$CB, $47	2F	X	X
bit 0,b	$CB, $40	2F	X	X
bit 0,c	$CB, $41	2F	X	X
bit 0,d	$CB, $42	2F	X	X
bit 0,e	$CB, $43	2F	X	X
bit 0,h	$CB, $44	2F	X	X
bit 0,l	$CB, $45	2F	X	X
bit 0,(hl)	$CB, $46	2F + 1R	3F + 1R	3F + 1R
bit 0,(ix+n)	$DD, $CB, n, $46	4F + 1R	5F + 1R	5F + 1R
bit 0,(iy+n)	$FD, $CB, n, $46	4F + 1R	5F + 1R	5F + 1R
bit 1,a	$CB, $4F	2F	X	X
bit 1,b	$CB, $48	2F	X	X
bit 1,c	$CB, $49	2F	X	X
bit 1,d	$CB, $4A	2F	X	X
bit 1,e	$CB, $4B	2F	X	X
bit 1,h	$CB, $4C	2F	X	X
bit 1,l	$CB, $4D	2F	X	X
bit 1,(hl)	$CB, $4E	2F + 1R	3F + 1R	3F + 1R
bit 1,(ix+n)	$DD, $CB, n, $4E	4F + 1R	5F + 1R	5F + 1R
bit 1,(iy+n)	$FD, $CB, n, $4E	4F + 1R	5F + 1R	5F + 1R
bit 2,a	$CB, $57	2F	X	X
bit 2,b	$CB, $50	2F	X	X
bit 2,c	$CB, $51	2F	X	X
bit 2,d	$CB, $52	2F	X	X
bit 2,e	$CB, $53	2F	X	X
bit 2,h	$CB, $54	2F	X	X
bit 2,l	$CB, $55	2F	X	X
bit 2,(hl)	$CB, $56	2F + 1R	3F + 1R	3F + 1R
bit 2,(ix+n)	$DD, $CB, n, $56	4F + 1R	5F + 1R	5F + 1R
bit 2,(iy+n)	$FD, $CB, n, $56	4F + 1R	5F + 1R	5F + 1R
bit 3,a	$CB, $5F	2F	X	X
bit 3,b	$CB, $58	2F	X	X
bit 3,c	$CB, $59	2F	X	X
bit 3,d	$CB, $5A	2F	X	X
bit 3,e	$CB, $5B	2F	X	X
bit 3,h	$CB, $5C	2F	X	X
bit 3,l	$CB, $5D	2F	X	X
bit 3,(hl)	$CB, $5E	2F + 1R	3F + 1R	3F + 1R
bit 3,(ix+n)	$DD, $CB, n, $5E	4F + 1R	5F + 1R	5F + 1R
bit 3,(iy+n)	$FD, $CB, n, $5E	4F + 1R	5F + 1R	5F + 1R
bit 4,a	$CB, $67	2F	X	X
bit 4,b	$CB, $60	2F	X	X
bit 4,c	$CB, $61	2F	X	X
bit 4,d	$CB, $62	2F	X	X
bit 4,e	$CB, $63	2F	X	X
bit 4,h	$CB, $64	2F	X	X
bit 4,l	$CB, $65	2F	X	X
bit 4,(hl)	$CB, $66	2F + 1R	3F + 1R	3F + 1R
bit 4,(ix+n)	$DD, $CB, n, $66	4F + 1R	5F + 1R	5F + 1R
bit 4,(iy+n)	$FD, $CB, n, $66	4F + 1R	5F + 1R	5F + 1R
bit 5,a	$CB, $6F	2F	X	X
bit 5,b	$CB, $68	2F	X	X
bit 5,c	$CB, $69	2F	X	X
bit 5,d	$CB, $6A	2F	X	X
bit 5,e	$CB, $6B	2F	X	X
bit 5,h	$CB, $6C	2F	X	X
bit 5,l	$CB, $6D	2F	X	X
bit 5,(hl)	$CB, $6E	2F + 1R	3F + 1R	3F + 1R
bit 5,(ix+n)	$DD, $CB, n, $6E	4F + 1R	5F + 1R	5F + 1R
bit 5,(iy+n)	$FD, $CB, n, $6E	4F + 1R	5F + 1R	5F + 1R
bit 6,a	$CB, $77	2F	X	X
bit 6,b	$CB, $70	2F	X	X
bit 6,c	$CB, $71	2F	X	X
bit 6,d	$CB, $72	2F	X	X
bit 6,e	$CB, $73	2F	X	X
bit 6,h	$CB, $74	2F	X	X
bit 6,l	$CB, $75	2F	X	X
bit 6,(hl)	$CB, $76	2F + 1R	3F + 1R	3F + 1R
bit 6,(ix+n)	$DD, $CB, n, $76	4F + 1R	5F + 1R	5F + 1R
bit 6,(iy+n)	$FD, $CB, n, $76	4F + 1R	5F + 1R	5F + 1R
bit 7,a	$CB, $7F	2F	X	X
bit 7,b	$CB, $78	2F	X	X
bit 7,c	$CB, $79	2F	X	X
bit 7,d	$CB, $7A	2F	X	X
bit 7,e	$CB, $7B	2F	X	X
bit 7,h	$CB, $7C	2F	X	X
bit 7,l	$CB, $7D	2F	X	X
bit 7,(hl)	$CB, $7E	2F + 1R	3F + 1R	3F + 1R
bit 7,(ix+n)	$DD, $CB, n, $7E	4F + 1R	5F + 1R	5F + 1R
bit 7,(iy+n)	$FD, $CB, n, $7E	4F + 1R	5F + 1R	5F + 1R

Notes

• Interestingly enough, the index registers IXH, IXL, IYH, and IYL cannot be used in this instruction, yet (IX+n) and (IY+n) are allowed as operands.

• The Z flag is set as follows:

  • Z means the bit is zero
  • NZ means the bit is one (non-zero)

See Also

RES, SET