Datasheet

 2010 Microchip Technology Inc. DS70138G-page 49
dsPIC30F3014/4013
6.0 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 5.5 “Control
Registers”, 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
typically requires 2 ms to complete, but the write time
varies 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. They are 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, allows 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 operation. In
these situations, following Reset, the user can check
the WRERR bit and rewrite the location. The address
register, NVMADR, remains unchanged.
6.1 Reading the Data EEPROM
A TBLRD instruction reads a word at the current
program word address. This example uses W0 as a
pointer to data EEPROM. The result is placed in
register W4 as shown in Example 6-1.
EXAMPLE 6-1: 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 “16-bit MCU and DSC Pro-
grammer’s Reference Manual”
(DS70157).
Note: Interrupt flag bit, NVMIF in the IFS0 regis-
ter, is set when the 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