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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 | |||
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PIC18F6520/8520/6620/8620/6720/8720
SUBWFB
Subtract W from f with Borrow
Syntax:
[ label ] SUBWFB f [,d [,a]
Operands:
0 ⤠f ⤠255
d â [0,1]
a â [0,1]
Operation:
(f) â (W) â (C) â dest
Status Affected: N, OV, C, DC, Z
Encoding:
0101 10da ffff ffff
Description:
Subtract W and the Carry flag
(borrow) from register âfâ (2âs com-
plement method). If âdâ is â0â, the
result is stored in W. If âdâ is â1â, the
result is stored back in register âfâ
(default). If âaâ is â0â, the Access
Bank will be selected, overriding the
BSR value. If âaâ is â1â, then the bank
will be selected as per the BSR
value (default).
Words:
1
Cycles:
1
Q Cycle Activity:
Q1
Q2
Decode
Read
register âfâ
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)
; [2âs 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 â [0,1]
a â [0,1]
(f<3:0>) â dest<7:4>,
(f<7:4>) â dest<3:0>
None
0011 10da ffff ffff
The upper and lower nibbles of
register âfâ are exchanged. If âdâ is
â0â, the result is placed in W. If âdâ is
â1â, the result is placed in register âfâ
(default). If âaâ is â0â, the Access
Bank will be selected, overriding
the BSR value. If âaâ is â1â, then the
bank will be selected as per the
BSR value (default).
1
Cycles:
1
Q Cycle Activity:
Q1
Q2
Decode
Read
register âfâ
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.
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