PIC16F874 datasheet(7/22 Pages) MICROCHIP

7 / 22 page

 2002 Microchip Technology Inc.

DS39025F-page 7

PIC16F87X

2.5

Erasing Program and Data

Memory

Depending on the state of the code protection bits, pro-

gram and data memory will be erased using different

procedures. The first set of procedures is used when

both program and data memories are not code pro-

tected. The second set of procedures must be used

when either memory is code protected. A device pro-

grammer should determine the state of the code pro-

tection bits and then apply the proper procedure to

erase the desired memory.

2.5.1

ERASING NON-CODE PROTECTED

PROGRAM AND DATA MEMORY

When both program and data memories are not code

protected, they must be individually erased using the

following procedures. The only way that both memories

are erased using a single procedure is if code protec-

tion is enabled for one of the memories. These proce-

dures do not erase the configuration word or ID

locations.

Procedure to bulk erase program memory:

Execute a Load Data for Program Memory com-

mand (000010) with a ’1’ in all locations

(0x3FFF)

Execute

Bulk

Erase

Setup1

command

(000001)

Execute

Bulk

Erase

Setup2

command

(000111)

Execute a Begin Erase/Programming command

(001000)

Wait 8 ms

Execute

Bulk

Erase

Setup1

command

(000001)

Execute

Bulk

Erase

Setup2

command

(000111)

Procedure to bulk erase data memory:

Execute a Load Data for Data Memory com-

mand (000011) with a ’1’ in all locations

(0x3FFF)

Execute

Bulk

Erase

Setup1

command

(000001)

Execute

Bulk

Erase

Setup2

command

(000111)

Execute a Begin Erase/Programming command

(001000)

Wait 8 ms

Execute

Bulk

Erase

Setup1

command

(000001)

Execute

Bulk

Erase

Setup2

command

(000111)

2.5.2

ERASING CODE PROTECTED

MEMORY

For the PIC16F87X devices, once code protection is

enabled, all protected program and data memory loca-

tions read all ’0’s and further programming is disabled.

The ID locations and configuration word read out

unscrambled and can be reprogrammed normally. The

only procedure to erase a PIC16F87X device that is

code protected is shown in the following procedure.

This method erases program memory, data memory,

configuration bits and ID locations. Since all data

within the program and data memory will be erased

when this procedure is executed, the security of

the data or code is not compromised.

Execute

Load

Configuration

command

(000000) with a ’1’ in all locations (0x3FFF)

Execute

Increment

Address

command

(000110) to set address to configuration word

location (0x2007)

Execute

Bulk

Erase

Setup1

command

(000001)

Execute

Bulk

Erase

Setup2

command

(000111)

Execute a Begin Erase/Programming command

(001000)

Wait 8 ms

Execute

Bulk

Erase

Setup1

command

(000001)

Execute

Bulk

Erase

Setup2

command

(000111)

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