The CD74HC154EN is a 4- to 16-line
decoder/demultiplexer with two enable inputs, E1 and E2..
A High on either enable input forces the output into the High
state. The demultiplexing function is performed by using the
four input lines, A0 to A3, to select the output lines Y0 to
Y15, and using one enable as the data input while holding
the other enable low.