The **74HC393D/T3** is a high-speed CMOS device featuring dual 4-stage binary ripple counters. It is widely used in digital electronics for frequency division, time-keeping, and counting applications. --- ## 1. Core Specifications and Features The 74HC393 series is known for its low power consumption and high-speed performance. Below are the primary technical characteristics: | Property | Specification | | :--- | :--- | | **Logic Family** | 74HC (High-speed CMOS) | | **Counter Type** | Dual 4-Bit Binary Ripple Counter | | **Supply Voltage (Vcc)** | 2.0V to 6.0V | | **Output Current** | ±5.2 mA | | **Maximum Frequency** | Up to 72 MHz (at 6V) | | **Operating Temperature** | -40°C to +125°C | | **Package Type** | SOIC-14 (indicated by the 'D' suffix) | --- ## 2. Pin Configuration and Functions The device contains two independent counters (Counter 1 and Counter 2). Each counter has its own clock input and master reset. ### Pinout Table | Pin Number | Symbol | Function | | :--- | :--- | :--- | | 1 | 1CP | Clock Input, Counter 1 (Negative-edge triggered) | | 2 | 1MR | Master Reset, Counter 1 (Active High) | | 3 to 6 | 1Q0 - 1Q3 | Parallel Outputs, Counter 1 | | 7 | GND | Ground (0V) | | 8 to 11 | 2Q3 - 2Q0 | Parallel Outputs, Counter 2 | | 12 | 2MR | Master Reset, Counter 2 (Active High) | | 13 | 2CP | Clock Input, Counter 2 (Negative-edge triggered) | | 14 | Vcc | Positive Supply Voltage | --- ## 3. Operational Logic ### Counting Mechanism The 74HC393 is a **ripple counter**. This means the clock signal only triggers the first flip-flop ($Q_0$). Each subsequent stage is triggered by the transition of the previous stage. * **Triggering:** The counter advances on the **HIGH-to-LOW** transition (negative edge) of the CP input. * **Resetting:** The Master Reset (MR) is asynchronous and active-HIGH. When MR is HIGH, all four output stages ($Q_0$ to $Q_3$) are forced to LOW, regardless of the clock input. ### Cascading Since there are two 4-bit counters in one chip, they can be cascaded to create an **8-bit counter** (counting up to 255). To do this: 1. Connect the clock signal to `1CP`. 2. Connect `1Q3` (the MSB of the first counter) to `2CP`. 3. The resulting output is read from `1Q0` (LSB) to `2Q3` (MSB). --- ## 4. Truth Table (Per Counter) | Master Reset (MR) | Clock (CP) | Output State | | :--- | :--- | :--- | | H | X | All Outputs Low (L) | | L | $\downarrow$ (Falling Edge) | Count Advances | | L | $\uparrow$ (Rising Edge) | No Change | --- ## 5. Typical Applications * **Frequency Dividers:** Dividing a clock signal by 2, 4, 8, or 16. * **Digital Clocks:** Used in timing circuits to track seconds, minutes, or hours. * **Address Generators:** For sequencing through memory addresses. * **Delay Lines:** Creating specific timing pulses in logic circuits.