8.1 In this Chapter

This chapter contains a description of the EEPROM memory as implemented in the HC11 and AVR families of microcontrollers, as well as a description of the EEPROM control registers, and software examples for erasing and programming the EEPROM.

8.2 Overwiew of the EEPROM Subsystem

In many situations it is required that some program parameters, calibration tables, etc. are stored in nonvolatile memory, able to keep its contents indefinitely after the system is powered off.

The solution to this problem is to include in the structure of the microcontroller an EEPROM memory area (Electrically Erasable Programmable Read Only Memory). Most modern microcontrollers include between 128 bytes and 2 kilobytes of EEPROM.

For technological reasons, erasing and programming the EEPROM requires a 20 V V _pp voltage, obtained by means of a so-called charge pump. The current capability of this internal source is very low, and therefore the charge pump requires a time of around 10 milliseconds to stabilize. The following restrictions apply when accessing the EEPROM:

• Before programming, an EEPROM bit must be erased. The value of an erased bit is 1.

• After an erase or program operation, a 10-ms delay is required for the charge pump to stabilize.

8.3 The EEPROM Memory and the CONFIG Register of HC11

Depending on the model, the microcontrollers of the HC11 family have between 512 and 2048 EEPROM memory bytes, mapped in the general memory map. The starting address of the EEPROM memory area differs from...