PIC18LC658-ESLASHCL datasheet(65/366 Pages) MICROCHIP

65 / 366 page

 2000 Microchip Technology Inc.

Advanced Information

DS30475A-page 65

PIC18CXX8

5.0

TABLE READS/TABLE WRITES

All PICmicro® devices have two memory spaces: the

program memory space and the data memory space.

Table Reads and Table Writes have been provided to

move data between these two memory spaces through

an 8-bit register (TABLAT).

The operations that allow the processor to move data

between the data and program memory spaces are:

• Table Read (TBLRD)

• Table Write (TBLWT)

Table Read operations retrieve data from program

memory and place it into the data memory space.

Figure 5-1 shows the operation of a Table Read with

program and data memory.

Table Write operations store data from the data mem-

ory space into program memory. Figure 5-2 shows the

operation of a Table Write with program and data

memory.

Table operations work with byte entities. A table block

containing data is not required to be word aligned, so a

table block can start and end at any byte address. If a

table write is being used to write an executable pro-

gram to program memory, program instructions will

need to be word aligned.

FIGURE 5-1:

TABLE READ OPERATION

FIGURE 5-2:

TABLE WRITE OPERATION

TABLE POINTER (1)

TABLE LATCH (8-bit)

PROGRAM MEMORY

TBLPTRH

TBLPTRL

TABLAT

TBLPTRU

Instruction: TBLRD*

Note 1:

Table Pointer points to a byte in program memory.

Program Memory

(TBLPTR)

TABLE POINTER (1)

TABLE LATCH (8-bit)

PROGRAM MEMORY

TBLPTRH

TBLPTRL

TABLAT

Program Memory

(TBLPTR)

TBLPTRU

Instruction: TBLWT*

Note 1:

Table Pointer points to a byte in program memory.

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