PIC18FXX20
BTFSC
Bit Test File, Skip if Clear
BTFSS
Bit Test File, Skip if Set
Syntax:
[ label ] BTFSC f,b[,a]
Syntax:
[ label ] BTFSS f,b[,a]
Operands:
0 ≤ f ≤ 255
0 ≤ b ≤ 7
a ∈ [0,1]
Operands:
0 ≤ f ≤ 255
0 ≤ b < 7
a ∈ [0,1]
Operation:
Status Affected:
Encoding:
skip if (f<b>) = 0
None
Operation:
Status Affected:
Encoding:
skip if (f<b>) = 1
None
1011
bbba
ffff
ffff
1010
bbba
ffff
ffff
Description:
If bit 'b' in register ‘f' is 0, then the
next instruction is skipped.
Description:
If bit 'b' in register 'f' is 1, then the
next instruction is skipped.
If bit 'b' is 0, then the next instruction
fetched during the current instruction
execution is discarded, and a NOPis
executed instead, making this a
two-cycle instruction. If ‘a’ is 0, the
Access Bank will be selected, over-
riding the BSR value. If ‘a’ = 1, then
the bank will be selected as per the
BSR value (default).
If bit 'b' is 1, then the next instruction
fetched during the current instruc-
tion execution, is discarded and a
NOPis executed instead, making this
a two-cycle instruction. If ‘a’ is 0, the
Access Bank will be selected, over-
riding the BSR value. If ‘a’ = 1, then
the bank will be selected as per the
BSR value (default).
Words:
Cycles:
1
1(2)
Words:
Cycles:
1
1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1
Q Cycle Activity:
Q1
Q2
Q3
Process Data
Q4
Q2
Q3
Process Data
Q4
Decode
Read
No
Decode
Read
No
register 'f'
operation
register 'f'
operation
If skip:
Q1
If skip:
Q1
Q2
Q3
Q4
Q2
Q3
Q4
No
No
No
No
No
No
No
No
operation
operation
operation
operation
operation
operation
operation
operation
If skip and followed by 2-word instruction:
If skip and followed by 2-word instruction:
Q1
Q2
No
Q3
No
Q4
Q1
Q2
No
Q3
No
Q4
No
operation
No
No
operation
No
operation
operation
operation
operation
operation
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
HERE
FALSE
TRUE
BTFSC
:
:
FLAG, 1, 0
HERE
FALSE
TRUE
BTFSS
:
:
FLAG, 1, 0
Example:
Example:
Before Instruction
PC
Before Instruction
PC
=
address (HERE)
=
address (HERE)
After Instruction
After Instruction
If FLAG<1>
PC
=
=
=
=
0;
If FLAG<1>
PC
=
=
=
=
0;
address (TRUE)
1;
address (FALSE)
1;
If FLAG<1>
PC
If FLAG<1>
PC
address (FALSE)
address (TRUE)
DS39609A-page 272
Advance Information
2003 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
