## Overview of the M93C74-RDS3 The **M93C74-RDS3** is a low-voltage, serial **Microwire EEPROM** (Electrically Erasable Programmable Read-Only Memory) manufactured by STMicroelectronics. It is designed for non-volatile data storage in applications where space and power consumption are critical. --- ### Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Memory Size** | 8 Kbit (8192 bits) | | **Organization** | Configurable as 1024 x 8-bit or 512 x 16-bit | | **Interface** | Microwire (3-wire serial interface) | | **Operating Voltage** | 1.8V to 5.5V | | **Clock Frequency** | 2 MHz (at 4.5V - 5.5V) / 1 MHz (at 1.8V) | | **Package Type** | TSSOP8 (Thin Shrink Small Outline Package) | | **Temperature Range** | -40°C to +125°C (Automotive Grade 3) | | **Endurance** | 1,000,000 Write Cycles | | **Data Retention** | 40 Years | --- ### Pin Configuration (TSSOP8) | Pin Name | Description | Function | | :--- | :--- | :--- | | **S** | Chip Select | Activates the device when high. | | **D** | Serial Data Input | Receives instructions and data. | | **Q** | Serial Data Output | Outputs data during read operations. | | **C** | Serial Clock | Synchronizes data transfer. | | **ORG** | Organization Select | High = 16-bit mode; Low = 8-bit mode. | | **VCC** | Supply Voltage | 1.8V to 5.5V power supply. | | **VSS** | Ground | Reference voltage (0V). | | **DU** | Don't Use | Should be left floating or tied to VSS. | --- ### Operational Features 1. **Microwire Protocol:** This is a synchronous serial communication interface developed by National Semiconductor. It uses three main lines: Clock (C), Data In (D), and Data Out (Q). 2. **Flexible Architecture:** The **ORG** pin allows the user to define the memory structure. If tied to $V_{CC}$, it behaves as 512 words of 16 bits. If tied to $V_{SS}$, it behaves as 1024 bytes of 8 bits. 3. **Self-Timed Write Cycles:** The device includes an internal timer to manage the write process. Once a write command is sent, the chip manages the erasing and programming of cells automatically. 4. **Ready/Busy Status:** During a write cycle, the Data Output (Q) pin can be polled to check if the internal programming is complete. 5. **Sequential Read:** It supports reading multiple memory locations sequentially by continuing to provide clock pulses after the initial address is read. --- ### Common Applications * **Automotive Electronics:** Storing calibration data and odometer readings. * **Industrial Controllers:** Configuration settings and error logging. * **Consumer Electronics:** User preferences and device ID storage.