PIC17C752 datasheet(57/328 Pages) MICROCHIP

57 / 328 page

DS30289A-page 57

PIC17C7XX

8.0

TABLE READS AND TABLE

WRITES

The PIC17C7XX has four instructions that allow the

processor to move data from the data memory space

to the program memory space, and vice versa. Since

the program memory space is 16-bits wide and the

data memory space is 8-bits wide, two operations are

required to move 16-bit values to/from the data mem-

ory.

The TLWT t,f and TABLWT t,i,f instructions are

used to write data from the data memory space to the

program

memory

space. The

TLRD

t,f

and

TABLRD

t,i,f

instructions are used to write data

from the program memory space to the data memory

space.

The program memory can be internal or external. For

the program memory access to be external, the device

needs to be operating in microprocessor or extended

microcontroller mode.

Figure 8-1 through Figure 8-4 show the operation of

these four instructions. The steps show the sequence

of operation.

FIGURE 8-1:

TLWT

INSTRUCTION

OPERATION

TABLE POINTER

TABLE LATCH (16-bit)

Program Memory

Data

Memory

TBLPTRH

TBLPTRL

TABLATH

TABLATL

TLWT 1,f

TLWT 0,f

Step 1: 8-bit value, from register 'f', loaded into the

high or low byte in TABLAT (16-bit).

FIGURE 8-2:

TABLWT

INSTRUCTION

OPERATION

TABLE POINTER

TABLE LATCH (16-bit)

Program Memory

Data

Memory

TBLPTRH

TBLPTRL

TABLATH

TABLATL

TABLWT 1,i,f

TABLWT 0,i,f

Prog-Mem

(TBLPTR)

Step 1: 8-bit value, from register 'f', loaded into the

high or low byte in TABLAT (16-bit).

2: 16-bit TABLAT value written to address Pro-

gram Memory (TBLPTR).

3: If “i” = 1, then TBLPTR = TBLPTR + 1,

If “i” = 0, then TBLPTR is unchanged.

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