12. Program EEPROM and Program Memory Control
12.1 General
The devices in this series have 4K words of program memory, the address range is from 0000h to 0FFFh,
which is read-only in all address ranges; the device has a 128-byte program EEPROM, and the address range
is 0000h to 007Fh, which is available in all address ranges. It can be read/write.
These memories are not directly mapped to the register file space, but indirectly addressed through the
special function register (SFR). A total of 6 SFR registers are used to access these memories：
⚫ EECON1
⚫ EECON2
⚫ EEDAT
⚫ EEDATH
⚫ EEADR
⚫ EEADRH
When accessing the program EEPROM, the EEDAT register stores 8-bit read/write data, and the EEADR
register stores the address of the program EEPROM unit being accessed.
When accessing the program memory of the device, the EEDAT and EEDATH register form a double
byte word to save the 16-bit data to be read, and the EEADR and EEADRH register form a double byte word
to save the 12-bit EEPROM cell address to be read.
Program memory allows reading in units of bytes. Program EEPROM allows byte read/write. A byte write
operation can automatically erase the target cell and write new data (erase before writing).
The writing time is controlled by the on-chip timer. The writing and erasing voltages are generated by the
on-chip charge pump, which is rated to work within the voltage range of the device for byte or word operations.
When the device is protected by code, the CPU can still continue to read/write the program EEPROM
and program memory. When the code is protected, the device programmer will no longer be able to access
the program EEPROM or program memory.
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