DM163006 datasheet(73/320 Pages) MICROCHIP

73 / 320 page

 2001 Microchip Technology Inc.

Advance Information

DS39541A-page 73

PIC18C601/801

6.0

TABLE READS/TABLE WRITES

PIC18C601/801 devices use two memory spaces: the

external program memory space and the data memory

space. Table Reads and Table Writes have been pro-

vided 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 external program memory

spaces are:

• Table Read (TBLRD)

• Table Write (TBLWT)

Table Read operations retrieve data from external pro-

gram memory and place it into the data memory space.

Figure 6-1 shows the operation of a Table Read with

program and data memory.

Table Write operations store data from the data mem-

ory space into external program memory. Figure 6-2

shows the operation of a Table Write with external pro-

gram 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 must

be word aligned.

FIGURE 6-1:

TABLE READ OPERATION

FIGURE 6-2:

TABLE WRITE OPERATION

Table Pointer(1)

Table Latch (8-bit)

External Program Memory

TBLPTRH

TBLPTRL

TABLAT

TBLPTRU

Instruction: TBLRD*

Note 1: Table Pointer points to a byte in external program memory.

Program Memory

(TBLPTR)

Table Pointer(1)

Table Latch (8-bit)

External Program Memory

TBLPTRH

TBLPTRL

TABLAT

External

(TBLPTR)

TBLPTRU

Instruction: TBLWT*

Note 1: Table Pointer points to a byte in external program memory.

Program Memory

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