DSPIC30F datasheet(71/248 Pages) MICROCHIP

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 2004 Microchip Technology Inc.

Preliminary

DS70083G-page 69

dsPIC30F

7.0

DATA EEPROM MEMORY

The Data EEPROM Memory is readable and writable

during normal operation over the entire V

DD range. The

data EEPROM memory is directly mapped in the

program memory address space.

The four SFRs used to read and write the program

Flash memory are used to access data EEPROM

memory, as well. As described in Section 6.5, these

registers are:

•NVMCON

•NVMADR

• NVMADRU

•NVMKEY

The EEPROM data memory allows read and write of

single words and 16-word blocks. When interfacing to

data memory, NVMADR in conjunction with the

NVMADRU register are used to address the EEPROM

location being accessed. TBLRDL and TBLWTL

instructions are used to read and write data EEPROM.

The dsPIC30F devices have up to 8 Kbytes (4K

words) of data EEPROM with an address range from

0x7FF000

to 0x7FFFFE.

A word write operation should be preceded by an erase

of the corresponding memory location(s). The write typ-

ically requires 2 ms to complete but the write time will

vary with voltage and temperature.

A program or erase operation on the data EEPROM

does not stop the instruction flow. The user is respon-

sible for waiting for the appropriate duration of time

before initiating another data EEPROM write/erase

operation. Attempting to read the data EEPROM while

a programming or erase operation is in progress results

in unspecified data.

Control bit WR initiates write operations similar to pro-

gram Flash writes. This bit cannot be cleared, only set,

in software. They are cleared in hardware at the com-

pletion of the write operation. The inability to clear the

WR bit in software prevents the accidental or

premature termination of a write operation.

The WREN bit, when set, will allow a write operation.

On power-up, the WREN bit is clear. The WRERR bit is

set when a write operation is interrupted by a MCLR

Reset or a WDT Time-out Reset during normal opera-

tion. In these situations, following Reset, the user can

check the WRERR bit and rewrite the location. The

address register NVMADR remains unchanged.

7.1

Reading the Data EEPROM

A TBLRD instruction reads a word at the current pro-

gram word address. This example uses W0 as a

pointer to data EEPROM. The result is placed in

EXAMPLE 7-1:

DATA EEPROM READ

Note: This data sheet summarizes features of this group

of dsPIC30F devices and is not intended to be a complete

reference source. For more information on the CPU,

peripherals, register descriptions and general device

functionality, refer to the dsPIC30F Family Reference

Manual (DS70046). For more information on the device

instruction set and programming, refer to the dsPIC30F

Programmer’s Reference Manual (DS70030).

Note:

Interrupt flag bit NVMIF in the IFS0 regis-

ter is set when write is complete. It must be

cleared in software.

MOV

#LOW_ADDR_WORD,W0

; Init Pointer

MOV

#HIGH_ADDR_WORD,W1

MOV

W1,TBLPAG

TBLRDL

[ W0 ], W4

; read data EEPROM

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