PIC18F2420/2520/4420/4520
CALLW
Subroutine Call Using WREG
MOVSF
Move Indexed to f
Syntax:
CALLW
None
Syntax:
MOVSF [z ], f
s
d
Operands:
Operation:
Operands:
0 ≤ z ≤ 127
s
0 ≤ f ≤ 4095
d
(PC + 2) → TOS,
(W) → PCL,
Operation:
((FSR2) + z ) → f
s
d
(PCLATH) → PCH,
(PCLATU) → PCU
Status Affected:
None
Encoding:
1st word (source)
2nd word (destin.)
Status Affected:
Encoding:
None
1110
1111
1011
ffff
0zzz
ffff
zzzz
ffff
s
0000
0000
0001
0100
d
Description
First, the return address (PC + 2) is
pushed onto the return stack. Next, the
contents of W are written to PCL; the
existing value is discarded. Then, the
contents of PCLATH and PCLATU are
latched into PCH and PCU,
respectively. The second cycle is
executed as a NOPinstruction while the
new next instruction is fetched.
Description:
The contents of the source register are
moved to destination register ‘f ’. The
d
actual address of the source register is
determined by adding the 7-bit literal
offset ‘z ’ in the first word to the value of
s
FSR2. The address of the destination
register is specified by the 12-bit literal
‘f ’ in the second word. Both addresses
d
can be anywhere in the 4096-byte data
space (000h to FFFh).
The MOVSFinstruction cannot use the
PCL, TOSU, TOSH or TOSL as the
destination register.
If the resultant source address points to
an indirect addressing register, the
value returned will be 00h.
Unlike CALL, there is no option to
update W, STATUS or BSR.
Words:
Cycles:
1
2
Q Cycle Activity:
Q1
Q2
Q3
Q4
Words:
Cycles:
2
2
Decode
Read
WREG
PUSH PC to
stack
No
operation
No
operation
No
operation
No
operation
No
operation
Q Cycle Activity:
Q1
Q2
Q3
Q4
Decode
Determine
Determine
Read
source addr source addr source reg
Example:
HERE
CALLW
Decode
No
operation
No
operation
Write
register ‘f’
(dest)
Before Instruction
PC
=
address (HERE)
PCLATH =
PCLATU =
10h
00h
06h
No dummy
read
W
=
After Instruction
PC
TOS
=
=
001006h
address (HERE + 2)
Example:
MOVSF
[05h], REG2
PCLATH =
PCLATU =
10h
00h
06h
Before Instruction
FSR2
=
80h
33h
W
=
Contents
of 85h
REG2
=
=
11h
After Instruction
FSR2
=
80h
Contents
of 85h
REG2
=
=
33h
33h
© 2008 Microchip Technology Inc.
DS39631E-page 311
MICROCHIP [ MICROCHIP ]
