18F8680 datasheet(91/496 Pages) MICROCHIP

91 / 496 page

 2004 Microchip Technology Inc.

DS30491C-page 89

PIC18F6585/8585/6680/8680

5.5

Writing to Flash Program Memory

The minimum programming block is 4 words or 8 bytes.

Word or byte programming is not supported.

Table writes are used internally to load the holding

registers needed to program the Flash memory. There

are eight holding registers used by the table writes for

programming.

Since the Table Latch (TABLAT) is only a single byte,

the TBLWT instruction has to be executed 8 times for

each programming operation. All of the table write

operations will essentially be short writes because only

the holding registers are written. At the end of updating

eight registers, the EECON1 register must be written

to, to start the programming operation with a long write.

The long write is necessary for programming the inter-

nal Flash. Instruction execution is halted while in a long

write cycle. The long write will be terminated by the

internal programming timer.

The EEPROM on-chip timer controls the write time.

The write/erase voltages are generated by an on-chip

charge pump, rated to operate over the voltage range

of the device for byte or word operations.

FIGURE 5-5:

TABLE WRITES TO FLASH PROGRAM MEMORY

Holding Register

TABLAT

Holding Register

TBLPTR = xxxxx7

Holding Register

TBLPTR = xxxxx1

Holding Register

TBLPTR = xxxxx0

Write Register

TBLPTR = xxxxx2

Program Memory

18F8680 데이터시트(PDF) 91 Page - Microchip Technology