## Technical Overview of M95256-RMW3P The **M95256-RMW3P** is a specific variant of the 256-Kbit serial SPI (Serial Peripheral Interface) EEPROM manufactured by **STMicroelectronics**. It is widely used for non-volatile data storage in industrial and consumer electronics. --- ### 1. Key Technical Specifications The part number defines specific electrical and physical characteristics: | Feature | Specification | | :--- | :--- | | **Memory Size** | 256 Kbit (32,768 x 8 bits) | | **Interface** | SPI (Mode 0 and Mode 3) | | **Clock Frequency** | Up to 20 MHz | | **Operating Voltage** | 1.8V to 5.5V | | **Package** | MLP8 (2x3 mm) or SO8N (depending on specific RMW suffix) | | **Operating Temperature** | -40°C to +125°C | | **Endurance** | 4 million write cycles | | **Data Retention** | 200 Years | --- ### 2. Part Number Breakdown Understanding the suffix codes is crucial for hardware design: * **M95256**: The base series (SPI EEPROM, 256 Kbit). * **-R**: Indicates the operating voltage range (1.8V to 5.5V). * **MW**: Represents the package type (typically **SO8N**, 150 mil width). * **3**: Represents the temperature range (**Range 3**: -40 to +125 °C). * **P**: Indicates **RoHS compliance** and Antimony-free/Halogen-free (Green). --- ### 3. Functional Pinout Typical for the SO8 package, the pin configuration is as follows: | Pin Number | Name | Function | | :--- | :--- | :--- | | 1 | **S#** | Chip Select (Active Low) | | 2 | **Q** | Serial Data Output (MISO) | | 3 | **W#** | Write Control (Hardware protection) | | 4 | **Vss** | Ground | | 5 | **D** | Serial Data Input (MOSI) | | 6 | **C** | Serial Clock | | 7 | **HOLD#** | Pause serial communication | | 8 | **Vcc** | Supply Voltage | --- ### 4. Logic & Programming Features * **Byte and Page Write**: Supports writing a single byte or a full page (64 bytes) in one cycle. * **Write Protection**: Includes a status register with software write protection and a hardware `W#` pin to prevent accidental data corruption. * **High-Speed Communication**: The 20 MHz clock speed allows for fast data retrieval compared to I2C-based EEPROMs. * **Low Power Consumption**: Consumes very little current in Standby mode (typically < 2 µA at 1.8V). --- ### 5. Implementation Example (C++ Pseudo-code) To read data from this chip using an MCU (like Arduino/STM32): ```cpp // Basic SPI Read sequence for M95256 void readEEPROM(uint16_t address) { digitalWrite(CHIP_SELECT, LOW); // Select the chip SPI.transfer(0x03); // Send READ Instruction SPI.transfer(address >> 8); // Send Address High Byte SPI.transfer(address & 0xFF); // Send Address Low Byte uint8_t data = SPI.transfer(0x00); // Clock out the data digitalWrite(CHIP_SELECT, HIGH); // Deselect } ```