PIC18F2420/2520/4420/4520
BCF
Bit Clear f
BN
Branch if Negative
Syntax:
BCF f, b {,a}
Syntax:
BN
n
Operands:
0 ≤ f ≤ 255
0 ≤ b ≤ 7
a ∈ [0,1]
Operands:
Operation:
-128 ≤ n ≤ 127
if Negative bit is ‘1’,
(PC) + 2 + 2n → PC
Operation:
0→ f<b>
Status Affected:
Encoding:
None
Status Affected:
Encoding:
None
1110
0110
nnnn
nnnn
1001
bbba
ffff
ffff
Description:
If the Negative bit is ‘1’, then the
Description:
Bit ‘b’ in register ‘f’ is cleared.
program will branch.
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank (default).
The 2’s complement number ‘2n’ is
added to the PC. Since the PC will have
incremented to fetch the next
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f ≤ 95 (5Fh). See
Section 24.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
instruction, the new address will be
PC + 2 + 2n. This instruction is then a
two-cycle instruction.
Words:
Cycles:
1
1(2)
Q Cycle Activity:
If Jump:
Words:
Cycles:
1
1
Q1
Q2
Q3
Q4
Decode
Read literal
‘n’
Process
Data
Write to PC
Q Cycle Activity:
Q1
Q2
Q3
Q4
No
No
No
No
Decode
Read
register ‘f’
Process
Data
Write
register ‘f’
operation
operation
operation
operation
If No Jump:
Q1
Q2
Q3
Q4
Example:
BCF
FLAG_REG, 7, 0
C7h
47h
Decode
Read literal
‘n’
Process
Data
No
operation
Before Instruction
FLAG_REG =
After Instruction
FLAG_REG =
Example:
HERE
BN Jump
Before Instruction
PC
=
address (HERE)
After Instruction
If Negative
PC
If Negative
PC
=
=
=
=
1;
address (Jump)
0;
address (HERE + 2)
DS39631E-page 276
© 2008 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
