PIC18F2331/2431/4331/4431
SLEEP
Enter Sleep Mode
SUBFWB
Subtract f from W with Borrow
Syntax:
[ label ] SLEEP
Syntax:
[ label ] SUBFWB f [,d [,a]]
Operands:
Operation:
None
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 the 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’. 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.
Description:
The Power-Down status bit (PD) is
cleared. The Time-out status bit (TO)
is set. Watchdog Timer and its post-
scaler are cleared.
The processor is put into Sleep mode
with the oscillator stopped.
Words:
Cycles:
1
1
Words:
Cycles:
1
1
Q Cycle Activity:
Q1
Q Cycle Activity:
Q1
Q2
Q3
Q4
Q2
Q3
Q4
Decode
No
operation
Process
Data
Go to
Sleep
Decode
Read
register ‘f’
Process
Data
Write to
destination
Example:
SLEEP
Example 1:
SUBFWB REG
Before Instruction
Before Instruction
TO
PD
=
=
?
?
REG
W
C
=
=
=
0x03
0x02
0x01
After Instruction
After Instruction
TO
PD
=
=
1 †
0
REG
W
C
Z
N
=
0xFF
0x02
0x00
0x00
=
=
=
=
†
If WDT causes wake-up, this bit is cleared.
0x01 ; result is negative
Example 2:
Before Instruction
SUBFWB
REG, 0, 0
REG
W
C
=
=
=
2
5
1
After Instruction
REG
W
C
Z
N
=
2
3
1
0
0
=
=
=
=
; result is positive
Example 3:
SUBFWB
REG, 1, 0
Before Instruction
REG
W
C
=
=
=
1
2
0
After Instruction
REG
W
C
Z
N
=
0
2
1
1
0
=
=
=
=
; result is zero
DS39616D-page 318
2010 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
