4 Kbit serial EEPROM for configuration and calibration storage
The Microchip 93AA66B-I/MS is a 4 Kbit serial EEPROM organized as 256 words of 16 bits each, accessed through a Microwire (3-wire) synchronous serial interface. It stores non-volatile configuration data, calibration constants, or small lookup tables in designs where a few hundred bytes of persistent memory is enough. The 2 MHz clock rate delivers read and write cycles fast enough for most power-on parameter loads and infrequent field updates.
The 6 ms write cycle time per word or page means the firmware must wait for the write-complete polling or a timed delay before the next access, a detail that matters when sequencing a multi-byte parameter save.