
PIC18FXX39
DS30485A-page 230
Preliminary
2002 Microchip Technology Inc.
DAW
Decimal Adjust W Register
Syntax:
[ label ] DAW
Operands:
None
Operation:
If [W<3:0> >9] or [DC = 1] then
(W<3:0>) + 6
→ W<3:0>;
else
(W<3:0>) → W<3:0>;
If [W<7:4> >9] or [C = 1] then
(W<7:4>) + 6 → W<7:4>;
else
(W<7:4>)
→ W<7:4>;
Status Affected:
C
Encoding:
0000
0111
Description:
DAW
adjusts the eight-bit value in
W, resulting from the earlier addi-
tion of two variables (each in
packed BCD format) and produces
a correct packed BCD result.
Words:
1
Cycles:
1
Q Cycle Activity:
Q1
Q2
Q3
Q4
Decode
Read
register W
Process
Data
Write
W
Example1:
DAW
Before Instruction
W=
0xA5
C=
0
DC
=
0
After Instruction
W
=
0x05
C=
1
DC
=
0
Example 2:
Before Instruction
W=
0xCE
C=
0
DC
=
0
After Instruction
W
=
0x34
C=
1
DC
=
0
DECF
Decrement f
Syntax:
[ label ] DECF f [,d [,a]
Operands:
0
≤ f ≤ 255
d
∈ [0,1]
a
∈ [0,1]
Operation:
(f) – 1
→ dest
Status Affected:
C, DC, N, OV, Z
Encoding:
0000
01da
ffff
Description:
Decrement register 'f'. If 'd' is 0, the
result is stored in W. If 'd' is 1, the
result is stored back in register 'f'
(default). 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
Q Cycle Activity:
Q1
Q2
Q3
Q4
Decode
Read
register 'f'
Process
Data
Write to
destination
Example:
DECF
CNT,
1, 0
Before Instruction
CNT
=
0x01
Z=
0
After Instruction
CNT
=
0x00
Z=
1