The Microchip 93C66B-I/MS is a 4 Kbit serial EEPROM using the three-wire Microwire interface, organized as 256 x 16 bits.
The 2 MHz clock rate is the Microwire bus speed, not a core oscillator — it sets the bit-transfer rate for read/write operations. For a 4 Kbit device that means a full-chip read completes in about 2 ms at 2 MHz, fast enough for calibration-parameter fetch at power-up or periodic sensor-trim updates. The 2 ms write cycle (word or page) is the time the part is busy after a write command; the host must wait or poll the READY/BUSY status before the next operation. In a system with a 5 V MCU running a 10 MHz SPI bus, the Microwire interface is slower but simpler — no complex command sequences, just chip select, clock, and data in/out.
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