PIC18FXX39 Datasheet, PDF (231/322 Pages) Microchip Technology – Enhanced FLASH Microcontrollers with Single Phase Induction Motor Control Kernel

PIC18FXX39
DECFSZ
Decrement f, skip if 0
Syntax:
Operands:
Operation:
Status Affected:
Encoding:
Description:
Words:
Cycles:
[ label ] DECFSZ f [,d [,a]]
0  f  255
d  [0,1]
a  [0,1]
(f) – 1  dest,
skip if result = 0
None
0010 11da ffff ffff
The contents of register 'f' are dec-
remented. If 'd' is 0, the result is
placed in W. If 'd' is 1, the result is
placed back in register 'f' (default).
If the result is 0, the next instruc-
tion, which is already fetched, is
discarded, and a NOP is executed
instead, making it a two-cycle
instruction. If ‘a’ is 0, the Access
Bank will be selected, overriding
the BSR value. If ‘a’ = 1, then the
bank will be selected as per the
BSR value (default).
1
1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1
Q2
Q3
Q4
Decode
Read
register 'f'
Process
Data
Write to
destination
If skip:
Q1
Q2
Q3
Q4
No
operation
No
operation
No
operation
No
operation
If skip and followed by 2-word instruction:
Q1
Q2
Q3
Q4
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
Example:
HERE
DECFSZ
GOTO
CONTINUE
CNT, 1, 1
LOOP
Before Instruction
PC
= Address (HERE)
After Instruction
CNT =
If CNT =
PC =
If CNT 
PC =
CNT - 1
0;
Address (CONTINUE)
0;
Address (HERE+2)
DCFSNZ
Decrement f, skip if not 0
Syntax:
Operands:
Operation:
Status Affected:
Encoding:
Description:
Words:
Cycles:
[ label ] DCFSNZ
0  f  255
d  [0,1]
a  [0,1]
(f) – 1  dest,
skip if result  0
None
f [,d [,a]
0100 11da ffff ffff
The contents of register 'f' are dec-
remented. If 'd' is 0, the result is
placed in W. If 'd' is 1, the result is
placed back in register 'f' (default).
If the result is not 0, the next
instruction, which is already
fetched, is discarded, and a NOP is
executed instead, making it a two-
cycle instruction. If ‘a’ is 0, the
Access Bank will be selected,
overriding the BSR value. If ‘a’ = 1,
then the bank will be selected as
per the BSR value (default).
1
1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1
Q2
Q3
Q4
Decode
Read
register 'f'
Process
Data
Write to
destination
If skip:
Q1
Q2
Q3
Q4
No
operation
No
operation
No
operation
No
operation
If skip and followed by 2-word instruction:
Q1
Q2
Q3
Q4
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
No
operation
Example:
HERE
ZERO
NZERO
DCFSNZ TEMP, 1, 0
:
:
Before Instruction
TEMP
After Instruction
TEMP
If TEMP
PC
If TEMP
PC
=?
= TEMP - 1,
= 0;
= Address (ZERO)
 0;
= Address (NZERO)
 2002-2013 Microchip Technology Inc.
Preliminary
DS30485B-page 231