PIC16F18323-ESLASHRFQTP datasheet(119/442 Pages) MICROCHIP

119 / 442 page

 2015 Microchip Technology Inc.

Preliminary

DS40001799A-page 119

PIC16(L)F18313/18323

10.4.6

MODIFYING PROGRAM FLASH

MEMORY

When modifying existing data in a program memory

row, and data within that row must be preserved, it must

first be read and saved in a RAM image. Program

memory is modified using the following steps:

Load the starting address of the row to be

modified.

Read the existing data from the row into a RAM

image.

Modify the RAM image to contain the new data

to be written into program memory.

Load the starting address of the row to be

rewritten.

Erase the program memory row.

Load the write latches with data from the RAM

image.

Initiate a programming operation.

FIGURE 10-6:

PROGRAM FLASH

MEMORY MODIFY

FLOWCHART

10.4.7

NVMREG EEPROM, USER ID,

DEVICE ID AND CONFIGURATION

WORD ACCESS

Instead of accessing Program Flash Memory, the

EEPROM, the User ID’s, Device ID/Revision ID and

Configuration

Words

can

accessed

when

NVMREGS = 1 in the NVMCON1 register. This is the

region that would be pointed to by PC<15> = 1, but not

all addresses are accessible. Different access may

exist for reads and writes. Refer to Table 10-3.

When read access is initiated on an address outside

the parameters listed in Table 10-3, the NVMDATH:

NVMDATL register pair is cleared, reading back ‘0’s.

Start

Modify Operation

Read Operation

(Figure x.x)

Erase Operation

(Figure x.x)

Modify Image

The words to be modified are

changed in the RAM image

End

Modify Operation

Write Operation

use RAM image

(Figure x.x)

An image of the entire row read

must be stored in RAM

Figure 10-1

Figure 10-3

Figure 10-5

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