How does a priority encoder differ from an ordinary encoder?
The correct answer and explanation is :
A priority encoder differs from an ordinary encoder primarily in how it handles multiple input signals that are active at the same time. In both cases, the encoder converts a set of binary inputs into a smaller binary output, typically representing the position of the highest-order active input. However, the key distinction lies in how the encoder prioritizes multiple simultaneous inputs.
Key Differences:
- Ordinary Encoder:
- An ordinary encoder is designed to convert a set of input lines into binary output, but it does not inherently prioritize which active input should be represented in the output if more than one input is active.
- For example, in a 4-to-2 encoder, if both input lines (e.g., I0 and I1) are active simultaneously, the encoder will output a code that may not necessarily correspond to the highest-order input, resulting in ambiguity or unpredictable behavior.
- Priority Encoder:
- A priority encoder, on the other hand, resolves this ambiguity by assigning priority to the inputs. It ensures that when multiple inputs are active, the encoder outputs the binary code corresponding to the highest-priority (highest-order) active input.
- For example, in a 4-to-2 priority encoder, if inputs I0, I1, and I3 are active simultaneously, the encoder will output the code corresponding to I3, as it has the highest priority.
- Additionally, priority encoders often include an output called “valid” or “active” to indicate whether any input is active.
Explanation:
The primary purpose of a priority encoder is to handle situations where multiple inputs could be active at the same time and ensure the encoder reliably outputs the binary code for the highest priority active input. This makes priority encoders more robust for systems where simultaneous inputs might occur, such as in interrupt handling or systems where several devices might request attention at once.
In contrast, an ordinary encoder simply generates an output based on the binary input signals without considering their relative priorities. This can lead to issues in systems where the distinction between simultaneous inputs matters, such as in digital control systems or safety-critical applications.
Thus, priority encoders are typically more suitable for applications requiring precise and unambiguous identification of the highest-priority input in the presence of multiple active signals.