PIC18F2420/2520/4420/4520
SUBFSR
Subtract Literal from FSR
SUBULNK
Subtract Literal from FSR2 and Return
Syntax:
SUBFSR f, k
0 ≤ k ≤ 63
f ∈ [ 0, 1, 2 ]
FSR(f) – k → FSRf
None
Syntax:
SUBULNK k
Operands:
Operands:
Operation:
0 ≤ k ≤ 63
FSR2 – k → FSR2,
(TOS) → PC
Operation:
Status Affected:
Encoding:
Status Affected: None
1110
1001
ffkk
kkkk
Encoding:
1110
1001
11kk
kkkk
Description:
The 6-bit literal ‘k’ is subtracted from
the contents of the FSR specified by
‘f’.
Description:
The 6-bit literal ‘k’ is subtracted from the
contents of the FSR2. A RETURNis then
executed by loading the PC with the TOS.
The instruction takes two cycles to
execute; a NOPis performed during the
second cycle.
This may be thought of as a special case of
the SUBFSRinstruction, where f = 3 (binary
‘11’); it operates only on FSR2.
Words:
1
1
Cycles:
Q Cycle Activity:
Q1
Q2
Q3
Q4
Decode
Read
register ‘f’
Process
Data
Write to
destination
Words:
1
2
Cycles:
Q Cycle Activity:
Q1
Example:
SUBFSR 2, 23h
03FFh
Q2
Q3
Q4
Before Instruction
FSR2
After Instruction
FSR2
Decode
Read
register ‘f’
Process
Data
Write to
destination
=
No
Operation
No
Operation
No
Operation
No
Operation
=
03DCh
Example:
SUBULNK 23h
Before Instruction
FSR2
PC
=
=
03FFh
0100h
After Instruction
FSR2
PC
=
=
03DCh
(TOS)
© 2008 Microchip Technology Inc.
DS39631E-page 313
MICROCHIP [ MICROCHIP ]
