### Technical Overview of TC74VHC164F The **TC74VHC164F** is a high-speed CMOS 8-bit Shift Register (Serial-in, Parallel-out) manufactured by Toshiba. It utilizes silicon gate CMOS technology to achieve high-speed operation similar to equivalent Bipolar Schottky TTL while maintaining the low power dissipation inherent to CMOS. --- ### Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Logic Type** | Shift Register (Serial to Parallel) | | **Number of Bits** | 8 Bits | | **Voltage Supply Range** | 2.0V to 5.5V | | **Propagation Delay** | 5.8 ns (at Vcc = 5V) | | **Output Current** | ±8 mA | | **Operating Temperature** | -40°C to 85°C | | **Package Type** | SOP-14 (Small Outline Package) | --- ### Core Functional Components 1. **Serial Inputs (A & B):** These are AND-gated inputs. Data is entered serially through either input; both must be HIGH for a logic "1" to be entered into the first stage of the register. 2. **Clock Input (CK):** Data is shifted on the **positive-going (rising) edge** of the clock pulse. 3. **Clear Input (CLR):** An active-low asynchronous input. When pulled LOW, it resets all internal flip-flops and sets all outputs (QA to QH) to LOW, regardless of the clock or data inputs. 4. **Parallel Outputs (QA to QH):** These 8 pins represent the current state of the register, allowing for parallel data processing. --- ### Logic Truth Table | Mode | CLR | CK | A | B | QA (Output 1) | QB...QH | | :--- | :---: | :---: | :---: | :---: | :---: | :---: | | **Reset** | L | X | X | X | L | L...L | | **Shift** | H | ↑ | L | X | L | QA0...QG0 | | **Shift** | H | ↑ | X | L | L | QA0...QG0 | | **Shift** | H | ↑ | H | H | H | QA0...QG0 | *Note: ↑ = Rising Edge, L = Low, H = High, X = Don't Care.* --- ### Typical Applications * **I/O Expansion:** Expanding the number of output pins on a microcontroller (e.g., Arduino/ESP32) using only 3 pins (Data, Clock, Clear). * **LED Drivers:** Controlling 7-segment displays or LED arrays. * **Data Conversion:** Converting serial data streams into parallel formats for bus communication. --- ### Circuit Example (Conceptual) ```cpp // Example: Shifting a byte to the TC74VHC164F void shiftOutData(uint8_t data) { for (int i = 0; i < 8; i++) { // Set Data Pin (A or B) based on bit digitalWrite(DATA_PIN, (data >> i) & 0x01); // Pulse the Clock digitalWrite(CLOCK_PIN, HIGH); digitalWrite(CLOCK_PIN, LOW); } } ```