PIC18CXX2_13 Datasheet, PDF (207/304 Pages) Microchip Technology – High Performance Microcontrollers with 10-bit A/D

PIC18CXX2
DECFSZ
Decrement f, skip if 0
Syntax:
[ label ] DECFSZ f [,d [,a]]
Operands:
0  f  255
d  [0,1]
a  [0,1]
Operation:
(f) – 1  dest,
skip if result = 0
Status Affected: None
Encoding:
0010 11da ffff ffff
Description:
The contents of register 'f' are
decremented. If 'd' is 0, the result is
placed in WREG. 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).
Words:
1
Cycles:
1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1
Q2
Decode
Read
register 'f'
If skip:
Q1
Q2
Q3
Process
Data
Q4
Write to
destination
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:
[label] DCFSNZ f [,d [,a]
Operands:
0  f  255
d  [0,1]
a  [0,1]
Operation:
(f) – 1  dest,
skip if result  0
Status Affected: None
Encoding:
0100 11da ffff ffff
Description:
The contents of register 'f' are dec-
remented. If 'd' is 0, the result is
placed in WREG. 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).
Words:
1
Cycles:
1(2)
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1
Q2
Decode
Read
register 'f'
If skip:
Q1
Q2
Q3
Process
Data
Q4
Write to
destination
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)
 1999-2013 Microchip Technology Inc.
DS39026D-page 207