70592C Datasheet, PDF (66/314 Pages) Microchip Technology – High-Performance, 16-bit Microcontrollers

PIC24HJXXXGPX06A/X08A/X10A
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. Erase the page (see Example 5-1):
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) Perform a dummy table write operation
(TBLWTL) to any address within the page
that needs to be erased.
d) Write 0x55 to NVMKEY.
e) Write 0xAA to NVMKEY.
f) Set the WR bit (NVMCON<15>). The erase
cycle begins and the CPU stalls for the dura-
tion 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
the program memory buffers (see Example 5-2).
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 mem-
ory 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
in Example 5-3.
EXAMPLE 5-1: ERASING A PROGRAM MEMORY PAGE
; Set up NVMCON for block erase operation
MOV
#0x4042, W0
MOV
W0, NVMCON
; Init pointer to row to be ERASED
MOV
#tblpage(PROG_ADDR), W0
MOV
W0, TBLPAG
MOV
#tbloffset(PROG_ADDR), W0
TBLWTL W0, [W0]
DISI #5
MOV
MOV
MOV
MOV
BSET
NOP
NOP
#0x55, W0
W0, NVMKEY
#0xAA, W1
W1, NVMKEY
NVMCON, #WR
;
; Initialize NVMCON
;
; Initialize PM Page Boundary SFR
; Initialize in-page EA<15:0> pointer
; Set base address of erase block
; Block all interrupts with priority <7
; for next 5 instructions
; Write the 55 key
;
; Write the AA key
; Start the erase sequence
; Insert two NOPs after the erase
; command is asserted
Note:
A program memory page erase operation
is set up by performing a dummy table
write (TBLWTL) operation to any address
within the page. This methodology is dif-
ferent from the page erase operation on
dsPIC30F/33F devices in which the erase
page was selected using a dedicated pair
of registers (NVMADRU and NVMADR).
DS70592C-page 66
© 2011 Microchip Technology Inc.