
2009 Microchip Technology Inc.
DS70286C-page 75
dsPIC33FJXXXGPX06/X08/X10
5.4.1
PROGRAMMING ALGORITHM FOR
FLASH PROGRAM MEMORY
The user can program one row of program Flash
memory at a time. To do this, it is necessary to erase
the 8-row erase page that contains the desired row.
The general process is:
1.
Read
eight
rows
of
program
memory
(512 instructions) and store in data RAM.
2.
Update the program data in RAM with the
desired new data.
3.
a) Set the NVMOP bits (NVMCON<3:0>) to
‘0010’ to configure for block erase. Set the
ERASE
(NVMCON<6>)
and
WREN
(NVMCON<14>) bits.
b) Write the starting address of the page to be
erased into the TBLPAG and W registers.
c)
Write 55h to NVMKEY.
d) Write AAh to NVMKEY.
e) Set the WR bit (NVMCON<15>). The erase
cycle begins and the CPU stalls for the
duration of the erase cycle. When the erase is
done, the WR bit is cleared automatically.
4.
Write the first 64 instructions from data RAM into
5.
Write the program block to Flash memory:
a) Set the NVMOP bits to ‘0001’ to configure
for row programming. Clear the ERASE bit
and set the WREN bit.
b) Write #0x55 to NVMKEY.
c)
Write #0xAA to NVMKEY.
d)
Set the WR bit. The programming cycle
begins and the CPU stalls for the duration of
the write cycle. When the write to Flash
memory is done, the WR bit is cleared
automatically.
6.
Repeat steps 4 and 5, using the next available
64 instructions from the block in data RAM by
incrementing the value in TBLPAG, until all
512 instructions are written back to Flash memory.
For protection against accidental operations, the write
initiate sequence for NVMKEY must be used to allow
any erase or program operation to proceed. After the
programming command has been executed, the user
must wait for the programming time until programming
is complete. The two instructions following the start of
the programming sequence should be NOPs, as shown
EXAMPLE 5-1:
ERASING A PROGRAM MEMORY PAGE
; Set up NVMCON for block erase operation
MOV
#0x4042, W0
;
MOV
W0, NVMCON
; Initialize NVMCON
; Init pointer to row to be ERASED
MOV
#tblpage(PROG_ADDR), W0
;
MOV
W0, TBLPAG
; Initialize PM Page Boundary SFR
MOV
#tbloffset(PROG_ADDR), W0
; Initialize in-page EA[15:0] pointer
TBLWTL
W0, [W0]
; Set base address of erase block
DISI
#5
; Block all interrupts with priority <7
; for next 5 instructions
MOV
#0x55, W0
MOV
W0, NVMKEY
; Write the 55 key
MOV
#0xAA, W1
;
MOV
W1, NVMKEY
; Write the AA key
BSET
NVMCON, #WR
; Start the erase sequence
NOP
; Insert two NOPs after the erase
NOP
; command is asserted