74154 4-16 DECODER/ DEMULTIPLEXER
Each of the 16 outputs can be connected through a resistor and then through an LED to serve as a simple 16 LED controller. The LED can be chosen at random by the status of the 4 line selector inputs. However, due to the internal structure of the 74154, only one output can be enabled at a time. This chip is often used in demultiplexing applications, such as digital clocks, LED matrices, and other graphical outputs. For example, if the target application requires 16 7-segment LED displays, but your microcontroller only has 4 lines to select which display is active, this chip (74LS154) would provide a very effective method of essentially multiplying you selecting lines by a 4 times. Understand, this is a typical example of application, not it's sole purpose. Download the datasheet below for a more comprehensive summary.
Each or these 4-line-to-16-line decoders utilizes TTL circuitry
to decode four binary-coded inputs into one of sixteen
mutually exclusive outputs when both the strobe inputs, G1
and G2, are low. The demultiplexing function is performed
by using the 4 input lines to address the output line, passing
data from one of the strobe inputs with the other strobe
input low. When either strobe input is high, all outputs are
high. These demultiplexers are ideally suited for implementing
high-performance memory decoders. All inputs are buffered
and input clamping diodes are provided to minimize
transmission-line effects and thereby simplify system design.