PIC18F87J11_12 Datasheet, PDF (385/466 Pages) Microchip Technology – 64/80-Pin, High-Performance, 1-Mbit Flash Microcontrollers

PIC18F87J11 FAMILY
TBLRD
Table Read
Syntax:
TBLRD ( *; *+; *-; +*)
Operands:
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(00A356h)
After Instruction
TABLAT
TBLPTR
= 55h
= 00A356h
= 34h
= 34h
= 00A357h
Example 2:
TBLRD +* ;
Before Instruction
TABLAT
TBLPTR
MEMORY(01A357h)
MEMORY(01A358h)
After Instruction
TABLAT
TBLPTR
= AAh
= 01A357h
= 12h
= 34h
= 34h
= 01A358h
 2007-2012 Microchip Technology Inc.
DS39778E-page 385