The Boolean logic will dictate which type of gate is used. In the case of the 8:3 priority encoder shown, only 3 4-input OR gates are needed. You could build the encoder using NAND gates, but I'm pretty sure you'd need a lot more gates.
The Boolean logic will dictate which type of gate is used. In the case of the 8:3 priority encoder shown, only 3 4-input OR gates are needed. You could build the encoder using NAND gates, but I'm pretty sure you'd need a lot more gates.
Yes, I know as a universal logic gate both NAND and NOR can do the same circuit implemented. But I am still willing to know why in encoder OR gate is used instead of AND gate? I am a simple theory of my own like: as "Encoder has higher numbers of inputs like 8 x 3 , so or gate do the job as it sums . On the other hand Decoder like 3x8 has higher numbers of output so it requres AND gate as it has common character to multiplication - So that If I use OR gate in Decoder, it will give always smaller number of outputs instead of Greater numbers of output!!!" -- Is my theory ok?
The number of inputs or outputs has no relevance to the type of logic gates required to build a boolean function. Every boolean expression has an equivalent gate type to realize that expression in hardware.
boolean + = logic OR
boolean * = logic AND
booleant not = logic not
All other logic functions can be constructed from these 3 basic equivalences.