EEPROM Memory Integration with Microchip 24LC64T-I/ST Serial I2C Interface

The integration of non-volatile memory is a fundamental requirement in modern electronic design, providing essential data retention for configuration parameters, user settings, and historical logs. The Microchip 24LC64T-I/ST stands as a prominent solution in this domain, offering 64 Kbits of Electrically Erasable Programmable Read-Only Memory (EEPROM) in a compact surface-mount package. Its utilization of the ubiquitous I2C (Inter-Integrated Circuit) serial protocol makes it an exceptionally versatile and widely compatible component for integration with a vast array of microcontrollers and processors.

This particular EEPROM model is organized as 8,192 words of 8 bits each, providing ample storage for a multitude of applications. A key advantage of the I2C interface is its simplicity, requiring only two bidirectional open-drain lines: Serial Data (SDA) and Serial Clock (SCL). This minimal pin count drastically reduces the wiring complexity and PCB real estate needed, making it ideal for space-constrained designs. The 24LC64T-I/ST supports a 400 kHz clock frequency, enabling efficient and sufficiently fast data transfer for most embedded scenarios. Furthermore, the device features hardware write-protection via its `WP` (Write Protect) pin. When this pin is tied to `VCC`, the entire memory array is locked against write operations, a crucial feature for safeguarding critical data from corruption.

The process of integrating this EEPROM into a system revolves around precise I2C communication. The microcontroller (the master) initiates communication by sending a start condition followed by a 7-bit device address (0b1010xxx). The three least significant bits (xxx) of this address are set by the state of the A0, A1, and A2 pins, allowing up to eight identical devices to be connected on the same I2C bus, thereby expanding the total available non-volatile memory without bus contention. After the address, the master sends a 16-bit memory address to specify the location within the EEPROM for the read or write operation.

For writing data, the master transmits the data bytes sequentially. The EEPROM features an internal page write buffer of 64 bytes, allowing for faster writes by loading an entire page of data before an internal self-timed write cycle commences. During this write cycle (which typically takes 5 ms), the device does not acknowledge its address, providing a simple method for the master to poll for completion. For reading data, the master can perform either a current address read, a random read (by first sending a dummy write sequence to set the address), or a sequential read to stream data from consecutive addresses continuously.

Successful integration requires careful attention to the I2C bus design. Pull-up resistors are mandatory on both the SDA and SCL lines to ensure the high logic level. Their values must be chosen based on the bus capacitance and desired speed to achieve signal integrity. Additionally, firmware routines must properly manage the internal write cycle timing, ensuring that the master does not attempt to communicate with the device before it has finished writing the data to its memory cells.

In summary, the 24LC64T-I/ST provides a robust, reliable, and simple method for adding non-volatile memory to any design.

ICGOODFIND: The Microchip 24LC64T-I/ST is an I2C-interfaced EEPROM that offers a perfect balance of sufficient density (64Kbit), simple two-wire interface, hardware write-protection, and multi-device support, making it an exceptionally versatile and engineer-friendly choice for data storage across countless applications.

Keywords: EEPROM, I2C Interface, Non-Volatile Memory, Microcontroller, Data Storage