PIC18FXX20
SUBWFB
Syntax:
Subtract W from f with Borrow
SWAPF
Swap f
Syntax:
[ label ] SWAPF f [,d [,a]
[ label ] SUBWFB 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<3:0>) → dest<7:4>,
(f<7:4>) → dest<3:0>
None
Operation:
Status Affected: N, OV, C, DC, Z
Encoding:
Description:
(f) – (W) – (C) → dest
Status Affected:
Encoding:
Description:
0101
10da
ffff
ffff
0011
10da
ffff
ffff
Subtract W and the carry flag (bor-
row) 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' (default). If ‘a’ is 0,
the Access Bank will be selected,
overriding the BSR value. If ‘a’ is 1,
then the bank will be selected as per
the BSR value (default).
The upper and lower nibbles of reg-
ister 'f' are exchanged. If 'd' is 0, the
result is placed in W. If 'd' is 1, the
result is placed in register 'f'
(default). If ‘a’ is 0, the Access
Bank will be selected, overriding
the BSR value. If ‘a’ is 1, then the
bank will be selected as per the
BSR value (default).
Words:
Cycles:
1
1
Words:
Cycles:
1
1
Q Cycle Activity:
Q1
Q Cycle Activity:
Q1
Q2
Q3
Process
Data
Q4
Q2
Q3
Process
Data
Q4
Decode
Read
Write to
Decode
Read
Write to
register 'f'
destination
register 'f'
destination
SUBWFB REG, 1, 0
Example 1:
Before Instruction
SWAPF
REG, 1, 0
Example:
REG
=
0x19
(0001 1001)
(0000 1101)
Before Instruction
W
C
=
0x0D
REG
=
0x53
0x35
=
1
After Instruction
After Instruction
REG
=
REG
=
=
0x0C
0x0D
(0000 1011)
(0000 1101)
W
C
=
=
=
1
0
0
Z
N
; result is positive
SUBWFB REG, 0, 0
Example 2:
Before Instruction
REG
=
0x1B
(0001 1011)
(0001 1010)
W
C
=
0x1A
=
0
After Instruction
REG
W
=
=
0x1B
0x00
(0001 1011)
C
Z
=
=
=
1
1
0
; result is zero
N
SUBWFB REG, 1, 0
Example 3:
Before Instruction
REG
=
0x03
(0000 0011)
(0000 1101)
W
C
=
0x0E
=
1
After Instruction
REG
=
0xF5
0x0E
(1111 0100)
; [2’s comp]
(0000 1101)
W
=
C
=
=
=
0
0
1
Z
N
; result is negative
DS39609A-page 296
Advance Information
2003 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
