PIC18F010 datasheet(49/176 Pages) MICROCHIP

49 / 176 page

 2001 Microchip Technology Inc.

Preliminary

DS41142A-page 47

PIC18F010/020

6.0

TABLE READ/WRITE

INSTRUCTIONS

The PIC18F010/020 has eight instructions that allow

the processor to move data from the data memory

space to the program memory space, and vice versa.

These eight instructions manipulate the Table Pointer

in a manner similar to the FSR’s.

The TBLRD instructions are used to read data from the

program memory space to the data memory space.

The TBLWT instructions are used to write data from the

data memory space to the program memory space.

6.1

Control Registers

A few control registers are used in conjunction with the

TBLRD

and TBLWT instructions. These include the:

• EECON1 register

• TABLAT register

• TBLPTR registers

6.1.1

EECON1 REGISTER

The EECON1 register holds bits to control erase and

write operations in FLASH memory. The EEPGD bit

selects data EEPROM, if clear, or program FLASH

memory, if set. The FREE bit is used to select erasing

versus writing to FLASH. The WREN bit enables writ-

ing. Finally, the WRERR bit indicates any errors. Refer

to Register 5-1 for details.

6.2

Table Reads from FLASH Program

Memory

Table Reads from program memory are performed one

byte at a time. The instruction will access one byte from

the program memory pointed to by the TBLPTR and

transfer that byte to the TABLAT. Figure 6-1 diagrams

the Table Read operation.

The TBLPTR can be updated in one of four ways,

based on the Table Read instructions:

• TBLRD* no-change

• TBLRD*+ post-increment

• TBLRD*- post-decrement

• TBLRD+* pre-increment

The internal program memory is normally word wide.

The Least Significant bit of the address selects between

the high and low bytes of the word. Figure 6-2 shows

the typical interface between the internal program

memory and the TABLAT.

FIGURE 6-1:

TBLRD*

INSTRUCTION OPERATION

Table Pointer

Table Latch (8-bit)

Program Memory

TBLPTRH

TBLPTRL

TABLAT

Prog-Mem

(TBLPTR)

TBLPTRU

Instruction: TBLRD*

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