DSPIC33FJ12MC02ESS datasheet(55/284 Pages) MICROCHIP

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Preliminary

DS70265B-page 53

dsPIC33FJ12MC201/202

4.4.1

PROGRAMMING ALGORITHM FOR

FLASH PROGRAM MEMORY

Programmers 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:

Read

eight

rows

program

memory

(512 instructions) and store in data RAM.

Update the program data in RAM with the

desired new data.

Erase the block (see Example 4-1):

Set the NVMOP bits (NVMCON<3:0>) to

‘0010’ to configure for block erase. Set the

ERASE (NVMCON<6>) and WREN

(NVMCON<14>) bits.

Write the starting address of the page to be

erased into the TBLPAG and W registers.

Write 0x55 to NVMKEY.

Write 0xAA to NVMKEY.

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.

Write the first 64 instructions from data RAM into

the program memory buffers (see Example 4-2).

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.

Write 0xAA to NVMKEY.

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.

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

application 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 4-3.

EXAMPLE 4-1:

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

; 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

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