PIC18F2480/2580/4480/4580
SUBWFB
Subtract W from f with Borrow
SWAPF
Swap f
Syntax:
SUBWFB f {,d {,a}}
Syntax:
SWAPF f {,d {,a}}
Operands:
0 ≤ f ≤ 255
d ∈ [0,1]
a ∈ [0,1]
Operands:
0 ≤ f ≤ 255
d ∈ [0,1]
a ∈ [0,1]
Operation:
(f) – (W) – (C) → dest
Operation:
(f<3:0>) → dest<7:4>,
(f<7:4>) → dest<3:0>
Status Affected:
Encoding:
N, OV, C, DC, Z
0101
10da
ffff
ffff
Status Affected:
Encoding:
None
Description:
Subtract W and the Carry flag (borrow)
from register ‘f’ (2’s complement
method). If ‘d’ is ‘0’, the result is stored
in W. If ‘d’ is ‘1’, the result is stored back
in register ‘f’.
0011
10da
ffff
ffff
Description:
The upper and lower nibbles of register
‘f’ are exchanged. If ‘d’ is ‘0’, the result
is placed in W. If ‘d’ is ‘1’, the result is
placed in register ‘f’.
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank.
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank.
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 26.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
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 26.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words:
Cycles:
1
1
Words:
1
1
Cycles:
Q Cycle Activity:
Q1
Q Cycle Activity:
Q1
Q2
Read
register ‘f’
Q3
Process
Data
Q4
Q2
Q3
Q4
Decode
Write to
destination
Decode
Read
register ‘f’
Process
Data
Write to
destination
Example 1:
SUBWFB REG, 1, 0
Before Instruction
REG
W
C
=
=
=
19h
0Dh
1
(0001 1001)
(0000 1101)
Example:
SWAPF
REG, 1, 0
Before Instruction
REG
After Instruction
=
53h
35h
After Instruction
REG
W
C
=
0Ch
0Dh
1
(0000 1011)
(0000 1101)
=
=
=
=
REG
=
Z
0
N
0
; result is positive
Example 2:
SUBWFB REG, 0, 0
Before Instruction
REG
W
C
=
=
=
1Bh
1Ah
0
(0001 1011)
(0001 1010)
After Instruction
REG
W
C
=
1Bh
00h
1
(0001 1011)
=
=
=
=
Z
1
; result is zero
N
0
Example 3:
Before Instruction
SUBWFB REG, 1, 0
REG
W
C
=
=
=
03h
0Eh
1
(0000 0011)
(0000 1101)
After Instruction
REG
=
F5h
(1111 0100)
; [2’s comp]
W
C
Z
=
=
=
=
0Eh
0
0
1
(0000 1101)
N
; result is negative
DS39637D-page 404
© 2009 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
