## MC74HC393D: Dual 4-Stage Binary Ripple Counter The **MC74HC393D** is a high-performance, silicon-gate CMOS device. It consists of two independent 4-bit binary ripple counters (total of 8 bits) with individual Clock ($CP$) and Master Reset ($MR$) inputs. ### 1. Key Specifications and Characteristics | Parameter | Specification | | :--- | :--- | | **Logic Family** | HC (High-speed CMOS) | | **Package Type** | SOIC-14 (indicated by the 'D' suffix) | | **Operating Voltage ($V_{CC}$)** | 2.0V to 6.0V | | **Counter Type** | Binary Ripple Counter | | **Number of Circuits** | 2 Independent Channels | | **Frequency ($f_{max}$)** | Up to 50 MHz (at 6.0V) | | **Output Current** | 4.0 mA | --- ### 2. Pin Configuration and Functions The device is housed in a 14-pin package. Below is the functional breakdown of the pins: | Pin Number | Symbol | Function | | :--- | :--- | :--- | | 1, 13 | $1CP, 2CP$ | **Clock Inputs:** Triggered on the High-to-Low transition (Negative Edge). | | 2, 12 | $1MR, 2MR$ | **Master Reset:** Active-High. Clears all counter stages to zero. | | 3-6 | $1Q_0 - 1Q_3$ | **Outputs (Counter 1):** Parallel binary outputs. | | 8-11 | $2Q_0 - 2Q_3$ | **Outputs (Counter 2):** Parallel binary outputs. | | 7 | $GND$ | Ground (0V). | | 14 | $V_{CC}$ | Positive Supply Voltage. | --- ### 3. Functional Logic and Operation #### Ripple Counter Mechanism Because this is a **ripple counter**, the clock signal only drives the first flip-flop ($Q_0$). Each subsequent flip-flop is clocked by the output of the preceding one. * **Advantage:** Simple design and low power consumption. * **Disadvantage:** Propagation delays accumulate; the outputs do not change simultaneously (asynchronous). #### Truth Table (Per Counter) | Clock ($CP$) | Reset ($MR$) | Output State | | :---: | :---: | :--- | | X | H | All Outputs = Low ($L$) | | $\downarrow$ | L | No Change | | $\uparrow$ | L | Count Advances | --- ### 4. Typical Applications * **Frequency Division:** Dividing a high-frequency clock down to lower frequencies (e.g., $1/2, 1/4, 1/8, 1/16$). * **Time Delays:** Generating specific timing intervals in digital circuits. * **Counters/Timers:** Used in digital clocks or event counters. * **Memory Addressing:** Sequential address generation for small memory blocks. --- ### 5. Circuit Implementation Example The following code snippet demonstrates how to define the behavior of an HC393-style counter in a Hardware Description Language (Verilog): ```verilog module hc393_behavioral ( input wire CP, // Clock (Negative Edge) input wire MR, // Master Reset (Active High) output reg [3:0] Q // 4-bit Output ); always @(negedge CP or posedge MR) begin if (MR) Q <= 4'b0000; else Q <= Q + 1; end endmodule ```