PIC18LF448T-E/SO 查看數據表（PDF） - Microchip Technology

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PIC18LF448T-E/SO

28/40-Pin High-Performance, Enhanced Flash Microcontrollers with CAN Module

Microchip Technology 

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

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

Q3

Decode

No

operation

No

operation

No

No operation

No

operation (Read Program operation

Memory)

Q4

No

operation

No operation

(Write

TABLAT)

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

© 2006 Microchip Technology Inc.

PIC18FXX8

DS41159E-page 319

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