DSPIC30F4012 datasheet(55/238 Pages) MICROCHIP

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DS70135G-page 55

dsPIC30F4011/4012

7.0

DATA EEPROM MEMORY

The data EEPROM memory is readable and writable

during normal operation over the entire VDD 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 6.0 “Flash

Program Memory”, 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, is used to address the EEPROM

location being accessed. TBLRDL and TBLWTL instruc-

tions are used to read and write data EEPROM. The

dsPIC30F4011/4012 devices have 1 Kbyte (512 words)

of data EEPROM, with an address range from

0x7FFC00 to 0x7FFFFE.

A word write operation should be preceded by an erase

of the corresponding memory location(s). The write

typically 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

program Flash writes. This bit cannot be cleared, only

set, in software. This bit is cleared in hardware at the

completion 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 oper-

ation. 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,

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 “16-bit MCU and DSC

Reference Manual” (DS70157).

Note:

Interrupt flag bit, NVMIF in the IFS0

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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