PIC18F2450 Datasheet, PDF (252/320 Pages) Microchip Technology – 28/40/44-Pin, High-Performance, 12 MIPS, Enhanced Flash, USB Microcontrollers with nanoWatt Technology

PIC18F2450/4450
TBLWT
Table Write
Syntax:
TBLWT ( *; *+; *-; +*)
Operands:
Operation:
None
if TBLWT*
(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
Status Affected: None
Encoding:
0000
0000
0000
11nn
nn=0 *
=1 *+
=2 *-
=3 +*
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.
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
Cycles:
2
Q Cycle Activity:
Q1
Q2
Q3
Q4
Decode No
No
No
operation operation operation
No
No
No
operation operation operation
(Read
TABLAT)
No
operation
(Write to
Holding
Register)
TBLWT
Table Write (Continued)
Example 1:
TBLWT *+;
Before Instruction
TABLAT
=
TBLPTR
=
HOLDING REGISTER
(00A356h)
=
55h
00A356h
FFh
After Instructions (table write completion)
TABLAT
=
TBLPTR
=
HOLDING REGISTER
(00A356h)
=
55h
00A357h
55h
Example 2:
TBLWT +*;
Before Instruction
TABLAT
=
TBLPTR
=
HOLDING REGISTER
(01389Ah)
=
34h
01389Ah
FFh
HOLDING REGISTER
(01389Bh)
= FFh
After Instruction (table write completion)
TABLAT
= 34h
TBLPTR
=
HOLDING REGISTER
(01389Ah)
=
HOLDING REGISTER
01389Bh
FFh
(01389Bh)
= 34h
DS39760A-page 250
Advance Information
© 2006 Microchip Technology Inc.