## Overview of the M95040-R The **M95040-R** is a 4-Kbit (512 x 8 bits) serial Electrically Erasable Programmable Read-Only Memory (EEPROM) manufactured by STMicroelectronics. It is designed for low-voltage applications and communicates via the **SPI (Serial Peripheral Interface)** bus. --- ### Technical Specifications The following table outlines the primary electrical and physical characteristics of the device: | Feature | Specification | | :--- | :--- | | **Memory Size** | 4 Kbits (512 Bytes) | | **Interface** | SPI (Mode 0 and Mode 3) | | **Operating Voltage ($V_{CC}$)** | 1.8V to 5.5V | | **Clock Frequency** | Up to 20 MHz (at 4.5V - 5.5V) | | **Page Size** | 16 Bytes | | **Write Cycles** | More than 4 million cycles | | **Data Retention** | More than 200 years | | **Operating Temperature** | -40°C to +85°C | --- ### Pin Configuration and Functions The device is typically available in SO8 or TSSOP8 packages. Below is the pinout description: 1. **$\bar{S}$ (Chip Select):** When low, the device is selected. When high, the device is deselected and in standby mode. 2. **$Q$ (Serial Data Output):** Used to transfer data out of the device during a Read operation. 3. **$\bar{W}$ (Write Protect):** Used to freeze the status register to prevent unauthorized write instructions. 4. **$V_{SS}$:** Ground. 5. **$D$ (Serial Data Input):** Used to transfer data into the device (op-codes, addresses, data). 6. **$C$ (Serial Clock):** Provides the timing for the serial interface. 7. **$\bar{HOLD}$:** Used to pause communication without resetting the chip select. 8. **$V_{CC}$:** Supply voltage. --- ### Internal Operations The M95040-R operates using a set of standard SPI instructions. Data is latched on the rising edge of the clock ($C$) for inputs and shifted out on the falling edge for outputs. #### 1. Status Register The device contains a Status Register that includes: * **WIP (Write In Progress) Bit:** Indicates if the memory is busy writing. * **WEL (Write Enable Latch) Bit:** Must be set before any Write instruction can be executed. * **Block Protect Bits (BP0, BP1):** Allows the user to software-protect a quarter, half, or the entire memory array. #### 2. Protocol Example (Read Sequence) To read data, the master device follows this logic: ```text 1. Pull Chip Select (S) LOW. 2. Send READ Instruction (0x03). 3. Send 8-bit Address. 4. Read data shifted out on Q. 5. Pull Chip Select (S) HIGH. ``` --- ### Key Applications * **Consumer Electronics:** Storing configuration settings in cameras or smart appliances. * **Industrial:** Storing calibration data and parameters for sensors. * **Medical:** Data logging for portable health monitors. * **Automotive:** (Note: Ensure the "R" grade matches specific AEC-Q100 requirements if used in vehicles).