PIC18FXX20 Datasheet, PDF (70/366 Pages) Microchip Technology – 64/80-Pin High Performance 1 Mbit Enhanced FLASH Microcontrollers with A/D

PIC18FXX20
5.5.1
FLASH PROGRAM MEMORY WRITE
SEQUENCE
The sequence of events for programming an internal
program memory location should be:
1. Read 64 bytes into RAM.
2. Update data values in RAM as necessary.
3. Load Table Pointer with address being erased.
4. Do the row erase procedure.
5. Load Table Pointer with address of first byte
being written.
6. Write the first 8 bytes into the holding registers
with auto-increment.
7. Set the EECON1 register for the write operation:
• set EEPGD bit to point to program memory;
• clear the CFGS bit to access program memory;
• set WREN to enable byte writes.
8. Disable interrupts.
9. Write 55h to EECON2.
10. Write AAh to EECON2.
11. Set the WR bit. This will begin the write cycle.
12. The CPU will stall for duration of the write (about
2 ms using internal timer).
13. Execute a NOP.
14. Re-enable interrupts.
15. Repeat steps 6-14 seven times, to write
64 bytes.
16. Verify the memory (Table Read).
This procedure will require about 18 ms to update one
row of 64 bytes of memory. An example of the required
code is given in Example 5-3.
Note:
Before setting the WR bit, the Table Pointer
address needs to be within the intended
address range of the eight bytes in the
holding register.
DS39609A-page 68
Advance Information
 2003 Microchip Technology Inc.