PIC24FV32KA304 datasheet(67/364 Pages) MICROCHIP

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DS39995D-page 67

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6.4.1.1

Data EEPROM Bulk Erase

To erase the entire data EEPROM (bulk erase), the

address registers do not need to be configured

because this operation affects the entire data

EEPROM. The following sequence helps in performing

a bulk erase:

Configure NVMCON to Bulk Erase mode.

Clear the NVMIF status bit and enable the NVM

interrupt (optional).

Write the key sequence to NVMKEY.

Set the WR bit to begin the erase cycle.

Either poll the WR bit or wait for the NVM

interrupt (NVMIF is set).

A typical bulk erase sequence is provided in

Example 6-3.

6.4.2

SINGLE-WORD WRITE

To write a single word in the data EEPROM, the

following sequence must be followed:

Erase one data EEPROM word (as mentioned in

the previous section) if the PGMONLY bit

(NVMCON<12>) is set to ‘1’.

Write the data word into the data EEPROM

latch.

Program the data word into the EEPROM:

- Configure the NVMCON register to program one

EEPROM word (NVMCON<5:0> = 0001xx).

- Clear the NVMIF status bit and enable the NVM

interrupt (optional).

- Write the key sequence to NVMKEY.

- Set the WR bit to begin the erase cycle.

- Either poll the WR bit or wait for the NVM

interrupt (NVMIF is set).

- To get cleared, wait until NVMIF is set.

A typical single-word write sequence is provided in

Example 6-4.

EXAMPLE 6-3:

DATA EEPROM BULK ERASE

EXAMPLE 6-4:

SINGLE-WORD WRITE TO DATA EEPROM

// Set up NVMCON to bulk erase the data EEPROM

NVMCON = 0x4050;

// Disable Interrupts For 5 Instructions

asm volatile ("disi #5");

// Issue Unlock Sequence and Start Erase Cycle

__builtin_write_NVM();

int __attribute__ ((space(eedata))) eeData = 0x1234;

int newData;

// New data to write to EEPROM

/*---------------------------------------------------------------------------------------------

The variable eeData must be a Global variable declared outside of any method

the code following this comment can be written inside the method that will execute the write

-----------------------------------------------------------------------------------------------

unsigned int offset;

// Set up NVMCON to erase one word of data EEPROM

NVMCON = 0x4004;

// Set up a pointer to the EEPROM location to be erased

TBLPAG = __builtin_tblpage(&eeData);

// Initialize EE Data page pointer

offset = __builtin_tbloffset(&eeData);

// Initizlize lower word of address

__builtin_tblwtl(offset, newData);

// Write EEPROM data to write latch

asm volatile ("disi #5");

// Disable Interrupts For 5 Instructions

__builtin_write_NVM();

// Issue Unlock Sequence & Start Write Cycle

while(NVMCONbits.WR=1);

// Optional: Poll WR bit to wait for

// write sequence to complete

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