logic diagram, 2-bit encoder

[mattlyons]

How would I draw a logic diagram of a 2-bit encoder, a circuit with four input lines, with exactly one of which is high at any instant, and two output lines whose 2-bit binary value tells which input is high?



Encoders have gone completely over my head in class from day one. Some major help is needed please.

 

[lostinxlation]

Truth table

in out
-----------
0001 : 00
0010 : 01
0100 : 10
1000 : 11
else : dont care

if one-hot is guaranteed on input,
out[1] = in[2] | in[3]
out[0] = in[1] | in[3]