PIC18F6585/8585/6680/8680
DS30491C-page 402
2004 Microchip Technology Inc.
SUBWFB
Subtract W from f with Borrow
Syntax:
[ label ] SUBWFB
f [,d [,a]]
Operands:
0
≤ f ≤ 255
d
∈ [0,1]
a
∈ [0,1]
Operation:
(f) – (W) – (C)
→ dest
Status Affected:
N, OV, C, DC, Z
Encoding:
0101
10da
ffff
Description:
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).
Words:
1
Cycles:
1
Q Cycle Activity:
Q1
Q2
Q3
Q4
Decode
Read
register ‘f’
Process
Data
Write to
destination
Example 1:
SUBWFB
REG, 1, 0
Before Instruction
REG
=
0x19
(0001 1001)
W
=
0x0D
(0000 1101)
C=
1
After Instruction
REG
=
0x0C
(0000 1011)
W
=
0x0D
(0000 1101)
C=
1
Z=
0
N
=
0
; result is positive
Example 2:
SUBWFB
REG, 0, 0
Before Instruction
REG
=
0x1B
(0001 1011)
W
=
0x1A
(0001 1010)
C=
0
After Instruction
REG
=
0x1B
(0001 1011)
W
=
0x00
C=
1
Z
=
1
; result is zero
N=
0
Example 3:
SUBWFB
REG, 1, 0
Before Instruction
REG
=
0x03
(0000 0011)
W
=
0x0E
(0000 1101)
C=
1
After Instruction
REG
=
0xF5
(1111 0100)
; [2’s comp]
W
=
0x0E
(0000 1101)
C=
0
Z=
0
N
=
1
; result is negative
SWAPF
Swap f
Syntax:
[ label ] SWAPF f [,d [,a]]
Operands:
0
≤ f ≤ 255
d
∈ [0,1]
a
∈ [0,1]
Operation:
(f<3:0>)
→ dest<7:4>,
(f<7:4>)
→ dest<3:0>
Status Affected:
None
Encoding:
0011
10da
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’
(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:
1
Cycles:
1
Q Cycle Activity:
Q1
Q2
Q3
Q4
Decode
Read
register ‘f’
Process
Data
Write to
destination
Example:
SWAPF
REG, 1, 0
Before Instruction
REG
=
0x53
After Instruction
REG
=
0x35