PIC18F1220ESLASHSSSQTP datasheet(231/308 Pages) MICROCHIP

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DS39605F-page 229

PIC18F1220/1320

TBLRD

Table Read

Syntax:

[ label ] 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

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:

Cycles:

Q Cycle Activity:

Decode

operation

No operation

(Read Program

Memory)

operation

No operation

(Write

TABLAT)

TBLRD

Table Read (Continued)

Example 1:

TBLRD

*+ ;

Before Instruction

TABLAT

0x55

TBLPTR

0x00A356

MEMORY(0x00A356)

0x34

After Instruction

TABLAT

0x34

TBLPTR

0x00A357

Example 2:

TBLRD

+* ;

Before Instruction

TABLAT

0xAA

TBLPTR

0x01A357

MEMORY(0x01A357)

0x12

MEMORY(0x01A358)

0x34

After Instruction

TABLAT

0x34

TBLPTR

0x01A358

PIC18F1220E/SSSQTP Datasheet(PDF) 231 Page - Microchip Technology

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