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All of the bit instructions in the MCS 251 architecture (Table A-7) have opcode A9, which serves
as an escape byte (similar to A5). The high nibble of byte 1 specifies the bit instruction, as given
in Table A-10.
Instruction
1
Bit Instr (dir8)
Table A-11. Byte 1 (High Nibble) for Bit Instructions
Table A-10. Bit Instructions
Byte 0( x )
Byte 1
A
9
xxxx
0 bit
xxxx
Bit Instruction
0001
JBC bit
0010
JB bit
0011
JNB bit
0111
ORL CY,bit
1000
ANL CY,bit
1001
MOV bit,CY
1010
MOV CY,bit
1011
CPL bit
1100
CLR bit
1101
SETB bit
1110
ORL CY, /bit
1111
ANL CY, /bit
INSTRUCTION SET REFERENCE
Byte 2
Byte 3
dir8 addr
rel addr
A-7
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