To Have and to Hold
Several mid-and high-range PIC devices feature a small FEPROM scratch-pad memory that can be controlled and accessed indirectly via Special-Purpose Registers (SPRs) in the same manner as other peripheral devices. An integral non-volatile scratchpad enables the programmer to read and modify static data, such as the odometer tally in a car, which needs to be retained in the absence of a power supply — see Example 12.3 on page 349. Although this facility can be implemented using an external EEPROM memory, such as the 24LC01 of Fig. 12.22 on page 350, where only a modest amount of non-volatile data needs to be stored, integral EEPROM storage increases reliability and reduces cost, size and power requirements.
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