PIC18F1220_07 Datasheet, PDF (231/308 Pages) Microchip Technology – 18/20/28-Pin High-Performance, Enhanced Flash Microcontrollers with 10-bit A/D and nanoWatt Technology

PIC18F1220/1320
TBLRD
Table Read
Syntax:
Operands:
[ label ] TBLRD ( *; *+; *-; +*)
None
Operation:
if TBLRD *,
(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;
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 TBLRD 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
Decode
No
operation
No
No operation
operation (Read Program
Memory)
Q3
No
operation
No
operation
Q4
No
operation
No operation
(Write
TABLAT)
TBLRD
Table Read (Continued)
Example 1:
TBLRD *+ ;
Before Instruction
TABLAT
=
TBLPTR
=
MEMORY(0x00A356) =
After Instruction
TABLAT
=
TBLPTR
=
Example 2:
TBLRD +* ;
Before Instruction
TABLAT
=
TBLPTR
=
MEMORY(0x01A357) =
MEMORY(0x01A358) =
After Instruction
TABLAT
=
TBLPTR
=
0x55
0x00A356
0x34
0x34
0x00A357
0xAA
0x01A357
0x12
0x34
0x34
0x01A358
© 2007 Microchip Technology Inc.
DS39605F-page 229