12.3 Data EEPROM Memory

The data EEPROM is a nonvolatile memory array, separate from the data RAM and program memory, which is used for long-term storage of program data. It is not directly mapped in either the register file or program memory space but is indirectly addressed through the Special Function Registers (SFRs). The EEPROM is readable and writable during normal operation over the entire VDD range.

Four SFRs are used to read and write to the data EEPROM. They are:

  • NVMCON1
  • NVMCON2
  • NVMDAT
  • NVMADR
Important: The high byte of NVMADR (NVMADRH) is only implemented on devices with more than 256 bytes of EEPROM.

The data EEPROM allows byte read and write. When interfacing to the data memory block, NVMDAT holds the 8-bit data for read/write and the NVMADR register holds the address of the EEPROM location being accessed.

The EEPROM data memory is rated for high erase/write cycle endurance. A byte write automatically erases the location and writes the new data (erase-before-write). The write time is controlled by an internal programming timer; it will vary with voltage and temperature as well as from chip-to-chip. Refer to the Data EEPROM Memory parameters in the electrical specifications section for the limits.