Microchip 93LC56BT-I/ST: A Deep Dive into the 2K SPI Microwire Serial EEPROM
The Microchip 93LC56BT-I/ST is a 2K-bit Microwire Serial Electrically Erasable PROM (EEPROM) organized as 128 x 8-bit or 64 x 16-bit. Housed in a compact 8-lead TSSOP package, this non-volatile memory solution is designed for a wide array of applications requiring reliable data storage with low power consumption and simple serial interfacing. Its combination of durability, ease of use, and Microwire/SPI compatibility makes it a versatile choice for designers.
Key Features and Electrical Characteristics
The 93LC56BT-I/ST operates on a single power supply voltage ranging from 2.5V to 5.5V, making it suitable for both 3.3V and 5V systems. It features low-power operation, with a standby current of just 1 µA (typical) and an active read current of 200 µA (typical at 5V), which is critical for battery-powered portable devices.
This EEPROM supports a 1 MHz clock rate for high-speed data transfer. It offers impressive endurance, capable of 1,000,000 erase/write cycles per cell, and boasts data retention of over 200 years, ensuring long-term reliability for stored parameters. The device includes essential write protection features such as software and hardware write control, preventing inadvertent data corruption.
Interface and Instruction Set
The device utilizes a simple 3-wire serial interface (CS, SK, DI) for communication, with a fourth line (DO) for data output. This interface is compatible with a subset of the SPI protocol, often referred to as Microwire or 3-wire SPI. The instruction set is concise and powerful, consisting of commands to:
READ: Read data from a specified memory address.
WRITE: Write data to a specified memory address.
WREN: Set the Write Enable Latch (a required step before any write operation).
WRDI: Reset the Write Enable Latch.
ERASE: Erase a specific memory location (set all bits to '1').
ERAL: Erase the entire memory array.
WRAL: Write to all memory locations.
The sequential read capability allows for efficient reading of consecutive memory addresses without needing to transmit the address for each byte, streamlining data retrieval.
Application Notes and Circuit Implementation
Integrating the 93LC56BT into a system is straightforward. The primary design considerations involve proper signal conditioning and sequencing. The chip select (CS) pin must be driven high to initiate an instruction and brought low upon completion. All data is clocked into the device on the rising edge of the serial clock (SK) and clocked out on the falling edge.
A critical practice in any embedded design is to implement a robust power-on reset (POR) circuit. This ensures the microcontroller does not attempt to communicate with the EEPROM before the supply voltage has stabilized to a valid level, preventing spurious commands. Furthermore, designers must always poll the ready/busy status after issuing a write or erase command. Instead of relying on a fixed delay, the microcontroller should check the state of the data output (DO) pin to confirm the internal write cycle is complete before sending the next instruction, maximizing efficiency and ensuring data integrity.
Typical applications include storing:
Calibration coefficients and configuration data in industrial systems.
User settings and personalization data in consumer electronics.
Security codes and metering data in smart appliances.
Non-volatile parameter storage in automotive modules.
The Microchip 93LC56BT-I/ST is a highly reliable and easy-to-use serial EEPROM solution. Its low-voltage operation, Microwire/SPI compatibility, and exceptional endurance make it an ideal choice for designers seeking a non-volatile memory component for space-constrained, power-sensitive applications across various industries.
Keywords: EEPROM, Microwire, SPI, Non-volatile Memory, Low-power
