PIC18F2220/2320/4220/4320
SUBWFB
Syntax:
Subtract W from f with Borrow
SUBWFB REG, 1, 0
Example 1:
Before Instruction
[ label ] SUBWFB f [,d [,a]]
REG
W
C
=
=
=
0x19
0x0D
0x01
(0001 1001)
(0000 1101)
Operands:
0 ≤ f ≤ 255
d ∈ [0,1]
a ∈ [0,1]
After Instruction
REG
W
C
Z
N
=
=
=
=
=
0x0C
0x0D
(0000 1011)
(0000 1101)
Operation:
(f) – (W) – (C) → dest
Status Affected: N, OV, C, DC, Z
0x01
0x00
0x00
Encoding:
0101
10da
ffff
ffff
; result is positive
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).
SUBWFB REG, 0, 0
Example 2:
Before Instruction
REG
W
C
=
=
=
0x1B
0x1A
0x00
(0001 1011)
(0001 1010)
After Instruction
REG
W
C
Z
N
=
=
=
=
=
0x1B
0x00
(0001 1011)
0x01
0x01
0x00
; result is zero
Words:
Cycles:
1
1
SUBWFB REG, 1, 0
Example 3:
Before Instruction
Q Cycle Activity:
Q1
REG
W
C
=
=
=
0x03
0x0E
0x01
(0000 0011)
(0000 1101)
Q2
Q3
Q4
Decode
Read
register ‘f’
Process
Data
Write to
destination
After Instruction
REG
=
0xF5
0x0E
(1111 0100)
; [2’s comp]
(0000 1101)
W
=
C
Z
N
=
=
=
0x00
0x00
0x01
; result is negative
DS39599C-page 292
2003 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
