PIC18F258-ESLASHLSQTP datasheet(322/402 Pages) MICROCHIP

322 / 402 page

PIC18FXX8

DS41159E-page 320

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.)

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

No operation

(Read

TABLAT)

operation

No 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

PIC18F258-E/LSQTP Datasheet(PDF) 322 Page - Microchip Technology

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