PIC18C242 MICROCHIP [Microchip Technology], PIC18C242 Datasheet - Page 231

• Manufacturer Part Number: PIC18C242
• Description: High-Performance Microcontrollers with 10-Bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

TBLRD
Syntax:
Operands:
Operation:
Status Affected: None
Encoding:
Description:
Words:
Cycles:
Q Cycle Activity:
7/99 Microchip Technology Inc.
operation
Decode
No
Q1
operation
operation
Memory)
Table Read
[ label ]
None
if TBLRD *,
(Prog Mem (TBLPTR))
TBLPTR - No Change;
if TBLRD *+,
(Prog Mem (TBLPTR))
(TBLPTR) +1
if TBLRD *-,
(Prog Mem (TBLPTR))
(TBLPTR) -1
if TBLRD +*,
(TBLPTR) +1
(Prog Mem (TBLPTR))
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.
The TBLRD instruction can modify the
value of TBLPTR as follows:
• no change
• post-increment
• post-decrement
• pre-increment
1
2
Program
(Read
No
No
Q2
0000
TBLPTR[0] = 0:Least
TBLPTR[0] = 1:Most
TBLRD ( *; *+; *-; +*)
operation
operation
0000
No
No
Q3
TBLPTR;
TBLPTR;
TBLPTR;
Byte of Program
Memory Word
Byte of Program
Memory Word
0000
operation
operation
TABLAT)
TABLAT;
TABLAT;
TABLAT;
TABLAT;
(Write
No
No
Q4
Significant
Significant
nn=0 *
10nn
=1 *+
=2 *-
=3 +*
Preliminary
TBLRD
Example1:
Example2:
Before Instruction
After Instruction
Before Instruction
After Instruction
TABLAT
TBLPTR
MEMORY(0x00A356)
TABLAT
TBLPTR
TABLAT
TBLPTR
MEMORY(0x01A357)
MEMORY(0x01A358)
TABLAT
TBLPTR
Table Read (cont’d)
TBLRD
TBLRD
PIC18CXX2
*+ ;
+* ;
=
=
=
=
=
=
=
=
=
=
=
DS39026B-page 231
0x55
0x00A356
0x34
0x34
0x00A357
0xAA
0x01A357
0x12
0x34
0x34
0x01A358