Datasheet

 1997 Microchip Technology Inc. DS30272A-page 75
PIC16C71X
COMF Complement f
Syntax: [
label ] COMF f,d
Operands: 0 ≤ f ≤ 127
d ∈ [0,1]
Operation: (f
) → (dest)
Status Affected: Z
Encoding:
00 1001 dfff ffff
Description:
The contents of register 'f' are comple-
mented. If 'd' is 0 the result is stored in
W. If 'd' is 1 the result is stored back in
register 'f'.
Words: 1
Cycles: 1
Q Cycle Activity: Q1 Q2 Q3 Q4
Decode Read
register
'f'
Process
data
Write to
dest
Example
COMF REG1,0
Before Instruction
REG1 = 0x13
After Instruction
REG1 = 0x13
W = 0xEC
DECF Decrement f
Syntax: [
label ] DECF f,d
Operands: 0 ≤ f ≤ 127
d ∈ [0,1]
Operation: (f) - 1 → (dest)
Status Affected: Z
Encoding:
00 0011 dfff ffff
Description:
Decrement register 'f'. If 'd' is 0 the
result is stored in the W register. If 'd'
is 1 the result is stored back in register
'f'
.
Words: 1
Cycles: 1
Q Cycle Activity: Q1 Q2 Q3 Q4
Decode Read
register
'f'
Process
data
Write to
dest
Example
DECF CNT, 1
Before Instruction
CNT = 0x01
Z = 0
After Instruction
CNT = 0x00
Z = 1
DECFSZ Decrement f, Skip if 0
Syntax: [
label ] DECFSZ f,d
Operands: 0 ≤ f ≤ 127
d ∈ [0,1]
Operation: (f) - 1 → (dest); skip if result = 0
Status Affected: None
Encoding:
00 1011 dfff ffff
Description:
The contents of register 'f' are decre-
mented. If 'd' is 0 the result is placed in
the W register. If 'd' is 1 the result is
placed back in register 'f'.
If the result is 1, the next instruction, is
executed. If the result is 0, then a NOP is
executed instead making it a 2T
CY
instruction.
Words: 1
Cycles: 1(2)
Q Cycle Activity: Q1 Q2 Q3 Q4
Decode Read
register
'f'
Process
data
Write to
dest
If Skip: (2nd Cycle)
Q1 Q2 Q3 Q4
NOP NOP NOP NOP
Example
HERE DECFSZ CNT, 1
GOTO LOOP
CONTINUE •
•
•
Before Instruction
PC = address HERE
After Instruction
CNT = CNT - 1
if CNT = 0,
PC = address CONTINUE
if CNT ≠ 0,
PC = address HERE+1