Datasheet

© 2006 Microchip Technology Inc. DS41159E-page 317
PIC18FXX8
SUBLW Subtract W from Literal
Syntax: [
label ]SUBLW k
Operands: 0 ≤ k ≤ 255
Operation: k – (W) → W
Status Affected: N, OV, C, DC, Z
Encoding: 0000 1000 kkkk kkkk
Description: W is subtracted from the eight-bit
literal ‘k’. The result is placed in W.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read
literal ‘k’
Process
Data
Write to W
Example 1:
SUBLW 0x02
Before Instruction
W=1
C=?
After Instruction
W=1
C = 1 ; result is positive
Z=0
N=0
Example 2:
SUBLW 0x02
Before Instruction
W=2
C=?
After Instruction
W=0
C = 1 ; result is zero
Z=1
N=0
Example 3:
SUBLW 0x02
Before Instruction
W=3
C=?
After Instruction
W = FF ; (2’s complement)
C = 0 ; result is negative
Z=0
N=1
SUBWF Subtract W from f
Syntax:
[
label ] SUBWF f [,d [,a]]
Operands: 0 ≤ f ≤ 255
d ∈ [0,1]
a ∈ [0,1]
Operation: (f) – (W) → dest
Status Affected: N, OV, C, DC, Z
Encoding: 0101 11da ffff ffff
Description: Subtract W 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:
SUBWF REG
Before Instruction
REG = 3
W=2
C=?
After Instruction
REG = 1
W=2
C = 1 ; result is positive
Z=0
N=0
Example 2:
SUBWF REG, W
Before Instruction
REG = 2
W=2
C=?
After Instruction
REG = 2
W=0
C = 1 ; result is zero
Z=1
N=0
Example 3:
SUBWF REG
Before Instruction
REG = 0x01
W = 0x02
C=?
After Instruction
REG = 0xFFh ;(2’s complement)
W = 0x02
C = 0x00 ; result is negative
Z = 0x00
N = 0x01