PIC18F6520-I Datasheet, PDF (298/380 Pages) Micrel Semiconductor – 64/80-Pin High-Performance, 256 Kbit to 1 Mbit Enhanced Flash Microcontrollers with A/D

PIC18F6520/8520/6620/8620/6720/8720
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 ffff
Description:
Subtract W and the Carry flag
(borrow) from register ‘f’ (2’s com-
plement 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
Decode
Read
register ‘f’
Q3
Process
Data
Q4
Write to
destination
Example 1:
SUBWFB REG, 1, 0
Before Instruction
REG
W
C
= 0x19
= 0x0D
=1
After Instruction
REG
W
C
Z
N
= 0x0C
= 0x0D
=1
=0
=0
(0001 1001)
(0000 1101)
(0000 1011)
(0000 1101)
; result is positive
Example 2:
SUBWFB REG, 0, 0
Before Instruction
REG
W
C
= 0x1B
= 0x1A
=0
After Instruction
REG
W
C
Z
N
= 0x1B
= 0x00
=1
=1
=0
(0001 1011)
(0001 1010)
(0001 1011)
; result is zero
Example 3:
SUBWFB REG, 1, 0
Before Instruction
REG
W
C
= 0x03
= 0x0E
=1
After Instruction
REG = 0xF5
W
= 0x0E
C
=0
Z
=0
N
=1
(0000 0011)
(0000 1101)
(1111 0100)
; [2’s comp]
(0000 1101)
; result is negative
SWAPF
Swap f
Syntax:
Operands:
Operation:
Status Affected:
Encoding:
Description:
Words:
[ label ] SWAPF f [,d [,a]
0 ≤ f ≤ 255
d ∈ [0,1]
a ∈ [0,1]
(f<3:0>) → dest<7:4>,
(f<7:4>) → dest<3:0>
None
0011 10da ffff ffff
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).
1
Cycles:
1
Q Cycle Activity:
Q1
Q2
Decode
Read
register ‘f’
Q3
Process
Data
Q4
Write to
destination
Example:
SWAPF REG, 1, 0
Before Instruction
REG = 0x53
After Instruction
REG = 0x35
DS39609B-page 296
 2004 Microchip Technology Inc.