IC 74147 – BCD to Decimal Priority Encoder

Overview

The IC 74147 is a BCD (Binary-Coded Decimal) to decimal priority encoder designed to convert a 4-bit binary number into its decimal equivalent. It features priority encoding, which means that if multiple inputs are active, it will encode the highest-priority input. This IC is useful in applications where priority-based encoding of input signals is required, such as in digital displays and data processing systems.

Features

• BCD to Decimal Encoding: Converts a 4-bit BCD input into a 4-bit binary output representing the decimal equivalent.
• Priority Encoding: Encodes the highest priority input if multiple inputs are active.
• Active-Low Inputs: Inputs are active-low, meaning a low signal on an input will be encoded.
• Decimal Output: Provides a 4-bit binary output corresponding to the decimal representation of the highest priority active input.
• TTL Compatible: Compatible with TTL logic levels for integration with other digital circuits.
• Enable Input: Allows the encoder to be disabled or enabled.

Pin Configuration

The IC 74147 is typically available in a 16-pin Dual In-line Package (DIP) with the following pin configuration:

• Pins 1-4: Inputs (I0-I3) for the BCD input signals. These are active-low inputs, meaning a logic low level will be considered active.
• Pin 5: Enable (E) input to enable or disable the encoder. When low, the encoder is enabled; when high, it is disabled.
• Pin 6: Carry Out (CO) output to indicate whether there is a valid input being encoded.
• Pins 7-10: Outputs (O0-O3) provide the 4-bit binary representation of the highest priority active input.
• Pin 11: Ground (GND).
• Pin 12: Positive Supply Voltage (Vcc).
• Pin 13: Priority Control (PR) input to control the priority of the inputs.
• Pin 14: Output Enable (OE) to enable or disable the output lines.
• Pins 15-16: Additional inputs or control lines, depending on the specific package or configuration.

Working Principle

1. Priority Encoding: The IC 74147 uses priority encoding to determine which input is active. If multiple inputs are active, the encoder will prioritize the highest input (e.g., I3 has higher priority over I2, I1, and I0).
2. BCD to Decimal Conversion: Converts the active BCD input into a 4-bit binary output representing the decimal number. For example, if input I2 is active, the output will represent the decimal value 2.
3. Enable and Output Control: The Enable (E) input allows control over whether the encoder is active. When enabled (E low), the encoder processes inputs and provides outputs. The Output Enable (OE) controls whether the output lines are active or in a high-impedance state.
4. Carry Out: The Carry Out (CO) signal indicates that a valid input is being encoded. It can be used to signal other parts of the system or to trigger additional processing.

Applications

• Digital Displays: Used in systems where BCD input needs to be converted to a binary output for display purposes.
• Data Processing: Encodes multiple input signals based on priority for further processing or decision-making.
• Encoders: Part of digital systems that require encoding of input signals into binary form.
• Priority Systems: Used in systems where priority-based signal handling is essential.

Example Circuit

• Digital Encoder: Connect BCD input signals to the IC 74147. The active input will be encoded into a binary output corresponding to the decimal value. This output can then be used to drive a digital display or other processing units.

Advantages

• Priority Encoding: Ensures that the highest priority input is always encoded, even when multiple inputs are active.
• BCD to Decimal Conversion: Provides a straightforward way to convert BCD inputs into binary outputs.
• TTL Compatible: Easily integrates with other TTL logic components in digital systems.

Conclusion

The IC 74147 is a reliable BCD to decimal priority encoder designed for converting BCD inputs into binary outputs with priority encoding. Its ability to handle multiple active inputs and provide accurate encoding makes it ideal for various digital and data processing applications. Whether used in digital displays, data processing systems, or priority-based encoding tasks, the IC 74147 offers effective and efficient performance.

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