PIC18F1220ESLASHSSSQTP datasheet(232/308 Pages) MICROCHIP

232 / 308 page

PIC18F1220/1320

DS39605F-page 230

TBLWT

Table Write

Syntax:

[ label ] TBLWT ( *; *+; *-; +*)

Operands:

None

Operation:

if TBLWT*,

(TABLAT)

→ Holding Register;

TBLPTR – No Change;

if TBLWT*+,

(TABLAT)

→ Holding Register;

(TBLPTR) + 1

→ TBLPTR;

if TBLWT*-,

(TABLAT)

→ Holding Register;

(TBLPTR) – 1

→ TBLPTR;

if TBLWT+*,

(TBLPTR) + 1

→ TBLPTR;

(TABLAT)

→ Holding Register;

Status Affected: None

Encoding:

0000

11nn

nn = 0*

= 1*+

= 2*-

= 3+*

Description:

This instruction uses the 3 LSBs of

TBLPTR to determine which of the

8 holding registers the TABLAT is

written to. The holding registers are

used to program the contents of

Program Memory (P.M.). (Refer

to Section 6.0 “Flash Program

Memory” for additional details on

programming Flash memory.)

The TBLPTR (a 21-bit pointer) points

to each byte in the program memory.

TBLPTR has a 2-Mbyte address

range. The LSb of the TBLPTR

selects which byte of the program

memory location to access.

TBLPTR[0] = 0: Least Significant

Byte of Program

Memory Word

TBLPTR[0] = 1: Most Significant

Byte of Program

Memory Word

The TBLWT instruction can modify the

value of TBLPTR as follows:

• no change

• post-increment

• post-decrement

• pre-increment

TBLWT

Table Write (Continued)

Words: 1

Cycles: 2

Q Cycle Activity:

Decode

operation

(Read

TABLAT)

operation

(Write to

Holding

Example 1:

TBLWT *+;

Before Instruction

TABLAT

0x55

TBLPTR

0x00A356

HOLDING REGISTER

(0x00A356)

0xFF

After Instructions (table write completion)

TABLAT

0x55

TBLPTR

0x00A357

HOLDING REGISTER

(0x00A356)

0x55

Example 2:

TBLWT +*;

Before Instruction

TABLAT

0x34

TBLPTR

0x01389A

HOLDING REGISTER

(0x01389A)

0xFF

HOLDING REGISTER

(0x01389B)

0xFF

After Instruction (table write completion)

TABLAT

0x34

TBLPTR

0x01389B

HOLDING REGISTER

(0x01389A)

0xFF

HOLDING REGISTER

(0x01389B)

0x34

PIC18F1220E/SSSQTP Datasheet(PDF) 232 Page - Microchip Technology

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