The **7140LA55J** is a high-speed, low-power **Asynchronous Dual-Port Static RAM (SRAM)**. It is designed to allow two independent processors or buses to access a shared memory space simultaneously. --- ## 1. Technical Specifications Below are the primary technical characteristics of the 7140LA55J: | Parameter | Specification | | :--- | :--- | | **Memory Size** | 8 Kbit (1K x 8 bits) | | **Access Time** | 55 ns (Nanoseconds) | | **Supply Voltage** | 5.0V (±10%) | | **Interface** | Parallel (Asynchronous) | | **Package Type** | PLCC-52 (Plastic Leaded Chip Carrier) | | **Technology** | CMOS (Low Power) | | **Operating Temp** | 0°C to +70°C (Commercial Grade) | --- ## 2. Key Internal Components & Features ### Dual-Port Architecture The chip features two completely independent sets of control, address, and I/O pins (Left Port and Right Port). This allows: * **Simultaneous Read/Write:** Both ports can read or write to any location in the memory at the same time. * **Arbitration Logic:** It includes "Busy" logic to manage contention if both ports attempt to write to the exact same memory location simultaneously. ### Functional Blocks 1. **Memory Array:** Organized as 1,024 words of 8 bits each. 2. **Address Decoders:** Independent decoders for the Left and Right ports. 3. **Interrupt Logic:** Provides a flags-based communication system between processors. 4. **Output Enable (OE):** Controls the output drivers to prevent bus contention. --- ## 3. Pinout Description (PLCC-52) While a 52-pin layout is complex, the pins are generally grouped into three functional categories: * **Address Pins (A0L-A9L / A0R-A9R):** Used to select one of the 1,024 memory locations. * **Data I/O (I/O 0L-7L / I/O 0R-7R):** The 8-bit bidirectional data paths for each port. * **Control Pins:** * **CE (Chip Enable):** Activates the port. * **R/W (Read/Write):** Determines the data direction. * **BUSY:** Signals when a port is attempting to access a location currently being accessed by the other port. * **INT (Interrupt):** Allows one port to signal the other. --- ## 4. Part Number Decoding Understanding the nomenclature helps in identifying equivalent parts: | Segment | Meaning | | :--- | :--- | | **7140** | Part series (1K x 8 Dual-Port RAM) | | **LA** | Low Power version | | **55** | 55ns Access Speed | | **J** | PLCC Package (Plastic Leaded Chip Carrier) | --- ## 5. Common Applications * **Multiprocessor Systems:** Bridging two different CPUs (e.g., a DSP and a Microcontroller). * **Buffer Memory:** Used in high-speed telecommunications or networking hardware. * **Real-time Data Acquisition:** Allowing a sensor interface to write data while a CPU reads it.