## HM-65642: High-Speed CMOS Static RAM The **HM-65642** is a monolithic CMOS Static Random Access Memory (SRAM) organized as 8,192 words by 8 bits (8K x 8). It was historically manufactured by Harris Semiconductor (now part of Renesas/Intersil). It is known for its low power consumption and high reliability, often used in industrial and military applications. --- ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Organization** | 8K x 8 (64K bits) | | **Technology** | CMOS (Low Power) | | **Supply Voltage (Vcc)** | 4.5V to 5.5V | | **Access Time** | 120ns to 450ns (Depending on Grade) | | **Operating Current** | 40mA to 70mA (Active) | | **Standby Current** | 50µA to 100µA (Typical) | | **Package Types** | 28-pin DIP, CerDIP, or SMD | --- ### 2. Functional Pin Description The device utilizes a standard JEDEC pinout for 8K x 8 SRAMs, making it compatible with many other chips. * **A0 - A12 (Address Inputs):** Used to select one of the 8,192 8-bit bytes in the memory array. * **DQ0 - DQ7 (Data Input/Output):** Bi-directional pins used to read data from or write data to the memory. * **$\overline{E}$ (Chip Enable):** When LOW, the device is selected. When HIGH, the device is in low-power standby mode. * **$\overline{G}$ (Output Enable):** Controls the output buffers during a Read cycle. * **$\overline{W}$ (Write Enable):** When LOW, data on the DQ pins is written into the selected memory location. --- ### 3. Operating Modes The operation of the HM-65642 is determined by the state of the control pins: | Mode | $\overline{E}$ | $\overline{G}$ | $\overline{W}$ | I/O Pin State | Power | | :--- | :--- | :--- | :--- | :--- | :--- | | **Standby** | H | X | X | High-Z | Minimum | | **Read** | L | L | H | Data Out | Active | | **Write** | L | X | L | Data In | Active | | **Output Disable** | L | H | H | High-Z | Active | --- ### 4. Critical Electronic Features 1. **Fully Static Operation:** Unlike DRAM, the HM-65642 does not require an external clock or refreshing circuitry to retain data. 2. **TTL Compatibility:** All inputs and outputs are directly compatible with TTL (Transistor-Transistor Logic) levels. 3. **Low Power Standby:** The CMOS technology allows the chip to draw very little current when not active, making it ideal for battery-backed data retention. 4. **Three-State Outputs:** The DQ pins enter a high-impedance state when the chip is deselected, allowing multiple chips to share the same data bus.