PIC24FV16KM204 Datasheet, PDF (70/336 Pages) Microchip Technology – General Purpose, 16-Bit Flash Microcontroller with XLP Technology Data Sheet

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5.5.1
PROGRAMMING ALGORITHM FOR
FLASH PROGRAM MEMORY
The user can program one row of Flash program
memory at a time by erasing the programmable row.
The general process is:
1. Read a row of program memory (32 instructions)
and store in data RAM.
2. Update the program data in RAM with the
desired new data.
3. Erase a row (see Example 5-1):
a) Set the NVMOP bits (NVMCON<5:0>) to
‘011000’ to configure for row erase. Set the
ERASE (NVMCON<6>) and WREN
(NVMCON<14>) bits.
b) Write the starting address of the block 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 32 instructions from data RAM into
the program memory buffers (see Example 5-1).
5. Write the program block to Flash memory:
a) Set the NVMOP bits to ‘000100’ to
configure for row programming. Clear the
ERASE bit and set the WREN bit.
b) Write 55h to NVMKEY.
c) Write AAh 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.
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
displayed in Example 5-5.
EXAMPLE 5-1: ERASING A PROGRAM MEMORY ROW – ASSEMBLY LANGUAGE CODE
; Set up NVMCON for row erase operation
MOV
#0x4058, 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
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
EXAMPLE 5-2: ERASING A PROGRAM MEMORY ROW – ‘C’ LANGUAGE CODE
// C example using MPLAB C30
int __attribute__ ((space(auto_psv))) progAddr = 0x1234;
unsigned int offset;
// Variable located in Pgm Memory, declared as a
// global variable
//Set up pointer to the first memory location to be written
TBLPAG = __builtin_tblpage(&progAddr);
offset = __builtin_tbloffset(&progAddr);
// Initialize PM Page Boundary SFR
// Initialize lower word of address
__builtin_tblwtl(offset, 0x0000);
NVMCON = 0x4058;
asm("DISI #5");
__builtin_write_NVM();
// Set base address of erase block
// with dummy latch write
// Initialize NVMCON
// Block all interrupts for next 5 instructions
// C30 function to perform unlock
// sequence and set WR
DS33030A-page 70
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