Datasheet

PIC18F45J10 FAMILY
DS39682E-page 76 © 2009 Microchip Technology Inc.
7.4 Erasing Flash Program Memory
The minimum erase block is 1024 bytes. Only through
the use of an external programmer, or through ICSP
control, can larger blocks of program memory be Bulk
Erased. Word Erase in the Flash array is not supported.
When initiating an erase sequence from the micro-
controller itself, a block of 1024 bytes of program
memory is erased. The Most Significant 7 bits of the
TBLPTR<21:10> point to the block being erased.
TBLPTR<9:0> are ignored.
The EECON1 register commands the erase operation.
The WREN bit must be set to enable write operations.
The FREE bit is set to select an erase operation.
For protection, the write initiate sequence for EECON2
must be used.
A long write is necessary for erasing the internal Flash.
Instruction execution is halted while in a long write
cycle. The long write will be terminated by the internal
programming timer.
7.4.1 FLASH PROGRAM MEMORY
ERASE SEQUENCE
The sequence of events for erasing a block of internal
program memory location is:
1. Load Table Pointer register with address of the
block being erased.
2. Set the WREN and FREE bits (EECON1<2,4>)
to enable the erase operation.
3. Disable interrupts.
4. Write 55h to EECON2.
5. Write 0AAh to EECON2.
6. Set the WR bit. This will begin the erase cycle.
7. The CPU will stall for duration of the erase for
T
IE (see parameter D133B).
8. Re-enable interrupts.
EXAMPLE 7-2: ERASING A FLASH PROGRAM MEMORY BLOCK
MOVLW CODE_ADDR_UPPER ; load TBLPTR with the base
MOVWF TBLPTRU ; address of the memory block
MOVLW CODE_ADDR_HIGH
MOVWF TBLPTRH
MOVLW CODE_ADDR_LOW
MOVWF TBLPTRL
ERASE_ROW
BSF EECON1, WREN ; enable write to memory
BSF EECON1, FREE ; enable Erase operation
BCF INTCON, GIE ; disable interrupts
Required MOVLW 55h
Sequence MOVWF EECON2 ; write 55h
MOVLW 0AAh
MOVWF EECON2 ; write 0AAh
BSF EECON1, WR ; start erase (CPU stall)
BSF INTCON, GIE ; re-enable interrupts