PIC18F2450/4450
TBLRD
Table Read
TBLRD
Example 1:
Before Instruction
Table Read (Continued)
Syntax:
TBLRD ( *; *+; *-; +*)
None
TBLRD *+ ;
Operands:
Operation:
TABLAT
=
=
=
55h
00A356h
34h
if TBLRD *
TBLPTR
(Prog Mem (TBLPTR)) → TABLAT;
TBLPTR – No Change;
if TBLRD *+
(Prog Mem (TBLPTR)) → TABLAT;
(TBLPTR) + 1 → TBLPTR;
if TBLRD *-
(Prog Mem (TBLPTR)) → TABLAT;
(TBLPTR) – 1 → TBLPTR;
if TBLRD +*
(TBLPTR) + 1 → TBLPTR;
(Prog Mem (TBLPTR)) → TABLAT
MEMORY (00A356h)
After Instruction
TABLAT
TBLPTR
=
=
34h
00A357h
Example 2:
TBLRD +* ;
Before Instruction
TABLAT
TBLPTR
=
=
=
=
AAh
01A357h
12h
MEMORY (01A357h)
MEMORY (01A358h)
After Instruction
34h
TABLAT
TBLPTR
=
=
34h
01A358h
Status Affected: None
Encoding:
0000
0000
0000
10nn
nn=0 *
=1 *+
=2 *-
=3 +*
Description:
This instruction is used to read the contents
of Program Memory (P.M.). To address the
program memory, a pointer called Table
Pointer (TBLPTR) is used.
The TBLPTR (a 21-bit pointer) points to
each byte in the program memory. TBLPTR
has a 2-Mbyte address range.
TBLPTR[0] = 0: Least Significant Byte of
Program Memory Word
TBLPTR[0] = 1: Most Significant Byte of
Program Memory Word
The TBLRDinstruction can modify the value
of TBLPTR as follows:
•
•
•
•
no change
post-increment
post-decrement
pre-increment
Words:
Cycles:
1
2
Q Cycle Activity:
Q1
Q2
No
Q3
No
Q4
Decode
No
operation
operation
operation
No
No operation
No
No operation
(Write
TABLAT)
operation (Read Program operation
Memory)
© 2006 Microchip Technology Inc.
Advance Information
DS39760A-page 249
MICROCHIP [ MICROCHIP ]
