PIC18F2420/2520/4420/4520
TBLWT
Table Write
TBLWT
Table Write (Continued)
Syntax:
TBLWT ( *; *+; *-; +*)
None
Example1:
TBLWT *+;
Operands:
Operation:
Before Instruction
if TBLWT*,
TABLAT
TBLPTR
HOLDING REGISTER
(00A356h)
=
=
55h
00A356h
(TABLAT) → Holding Register,
TBLPTR – No Change;
if TBLWT*+,
(TABLAT) → Holding Register,
(TBLPTR) + 1→ TBLPTR;
if TBLWT*-,
(TABLAT) → Holding Register,
(TBLPTR) – 1→ TBLPTR;
if TBLWT+*,
(TBLPTR) + 1→ TBLPTR,
(TABLAT) → Holding Register
=
FFh
After Instructions (table write completion)
TABLAT
TBLPTR
HOLDING REGISTER
(00A356h)
=
=
55h
00A357h
=
55h
Example 2:
TBLWT +*;
Before Instruction
TABLAT
TBLPTR
HOLDING REGISTER
(01389Ah)
HOLDING REGISTER
(01389Bh)
=
=
34h
01389Ah
Status Affected: None
=
=
FFh
FFh
Encoding:
0000
0000
0000
11nn
nn=0 *
=1 *+
=2 *-
=3 +*
After Instruction (table write completion)
TABLAT
TBLPTR
=
=
34h
01389Bh
HOLDING REGISTER
(01389Ah)
HOLDING REGISTER
(01389Bh)
Description:
This instruction uses the 3 LSBs of
TBLPTR to determine which of the
8 holding registers the TABLAT is written
to. The holding registers are used to
program the contents of Program
Memory (P.M.). (Refer to Section 6.0
“Flash Program Memory” for additional
details on programming Flash memory.)
The TBLPTR (a 21-bit pointer) points to
each byte in the program memory.
TBLPTR has a 2-MByte address range.
The LSb of the TBLPTR selects which
byte of the program memory location to
access.
=
=
FFh
34h
TBLPTR<0> = 0:Least Significant
Byte of Program
Memory Word
TBLPTR<0> = 1:Most Significant
Byte of Program
Memory Word
The TBLWT instruction can modify the
value of TBLPTR as follows:
•
•
•
•
no change
post-increment
post-decrement
pre-increment
Words:
1
2
Cycles:
Q Cycle Activity:
Q1
Q2
No
Q3
No
Q4
No
Decode
operation operation operation
No
No No No
operation operation operation operation
(Read
TABLAT)
(Write to
Holding
Register )
DS39631E-page 306
© 2008 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
