Page 94 - Handout Digital Electronics

From the logic expressions, we produce the 8 to 3 binary encoder logic circuits

The xo input line is just earthed as it is insignificant here.

Figure 27: 8 to 3 encoder logic circuit

11.3 Priority encoder
A priority encoder is a combinational logic circuit that compresses multiple binary data inputs into a
small number of outputs. The output of a priority encoder is the binary representation of the ordinary
number starting from zero of the most significant input bits. Priority encoders are often used to control
interruptive requests by acting on the highest priority request. It also includes a priority function, for
example if two or more priority request input signals are equal to one (1) at the same time, the input
signal having the highest priority will take precedence. The internal hardware will check this condition
and a priority is set.

Consider the logic circuit of a priority encoder below:

Figure 28: Priority encoder logic circuit

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