PIC18F2220/2320/4220/4320
TBLWT
Table Write
TBLWT Table Write (Continued)
Syntax:
[ label ]
TBLWT ( *; *+; *-; +*)
Words: 1
Cycles: 2
Q Cycle Activity:
Q1
Operands:
Operation:
None
if TBLWT*,
(TABLAT) → Holding Register;
TBLPTR - No Change;
if TBLWT*+,
Q2
Q3
Q4
Decode
No
No
No
operation
operation
operation
(TABLAT) → Holding Register;
(TBLPTR) +1 → TBLPTR;
if TBLWT*-,
(TABLAT) → Holding Register;
(TBLPTR) -1 → TBLPTR;
if TBLWT+*,
No
operation
No
operation
(Read
No
operation
No
operation
(Write to
Holding
Register )
TABLAT)
(TBLPTR) +1 → TBLPTR;
(TABLAT) → Holding Register;
Example1:
TBLWT *+;
Status Affected: None
Before Instruction
0000
0000
0000
11nn
nn=0 *
=1 *+
=2 *-
=3 +*
Encoding:
TABLAT
TBLPTR
HOLDING REGISTER
(0x00A356)
=
=
0x55
0x00A356
=
0xFF
After Instructions (table write completion)
TABLAT
=
0x55
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 MBtye address
range. The LSb of the TBLPTR selects
which byte of the program memory
location to access.
TBLPTR
=
0x00A357
HOLDING REGISTER
(0x00A356)
=
0x55
Example 2:
TBLWT +*;
Before Instruction
TABLAT
TBLPTR
HOLDING REGISTER
(0x01389A)
HOLDING REGISTER
(0x01389B)
=
=
0x34
0x01389A
=
=
0xFF
0xFF
After Instruction (table write completion)
TABLAT
TBLPTR
HOLDING REGISTER
(0x01389A)
HOLDING REGISTER
(0x01389B)
=
=
0x34
0x01389B
=
=
0xFF
0x34
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
2003 Microchip Technology Inc.
DS39599C-page 295
MICROCHIP [ MICROCHIP ]
