PIC18F2450/4450
SLEEP
Enter Sleep mode
SUBFWB
Subtract f from W with Borrow
Syntax:
SLEEP
None
Syntax:
SUBFWB f {,d {,a}}
Operands:
Operation:
Operands:
0 ≤ f ≤ 255
d ∈ [0,1]
a ∈ [0,1]
00h → WDT,
0 → WDT postscaler,
1 → TO,
Operation:
(W) – (f) – (C) → dest
0 → PD
Status Affected:
Encoding:
N, OV, C, DC, Z
Status Affected:
Encoding:
TO, PD
0101
01da
ffff
ffff
0000
0000
0000
0011
Description:
Subtract register ‘f’ and Carry flag
(borrow) from W (2’s complement
method). If ‘d’ is ‘0’, the result is stored
in W. If ‘d’ is ‘1’, the result is stored in
register ‘f’ (default).
Description:
The Power-Down status bit (PD) is
cleared. The Time-out status bit (TO)
is set. Watchdog Timer and its
postscaler are cleared.
If ‘a’ is ‘0’, the Access Bank is
selected. If ‘a’ is ‘1’, the BSR is used
to select the GPR bank (default).
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction
operates in Indexed Literal Offset
Addressing mode whenever
f ≤ 95 (5Fh). See Section 19.2.3
“Byte-Oriented and Bit-Oriented
Instructions in Indexed Literal Offset
Mode” for details.
The processor is put into Sleep mode
with the oscillator stopped.
Words:
Cycles:
1
1
Q Cycle Activity:
Q1
Q2
Q3
Q4
Decode
No
operation
Process
Data
Go to
Sleep
Example:
SLEEP
Words:
Cycles:
1
1
Before Instruction
TO
PD
=
=
?
?
Q Cycle Activity:
Q1
Q2
Q3
Q4
After Instruction
Decode
Read
register ‘f’
Process
Data
Write to
destination
TO
PD
=
=
1 †
0
Example 1:
SUBFWB
REG, 1, 0
†
If WDT causes wake-up, this bit is cleared.
Before Instruction
REG
W
C
=
=
=
3
2
1
After Instruction
REG
W
C
=
FF
2
=
=
=
=
0
Z
0
1
N
; result is negative
Example 2:
SUBFWB
REG, 0, 0
Before Instruction
REG
W
=
=
=
2
5
1
C
After Instruction
REG
W
C
=
2
3
1
0
=
=
=
=
Z
N
0
; result is positive
Example 3:
SUBFWB
REG, 1, 0
Before Instruction
REG
W
=
=
=
1
2
0
C
After Instruction
REG
W
C
=
0
2
1
1
0
=
=
=
=
Z
; result is zero
N
DS39760A-page 246
Advance Information
© 2006 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
