1. Eng. Mohammed Timraz Electronics & Communication Engineer University of Palestine Faculty of Engineering and Urban planning Software Engineering Department Computer Architecture Lab. ESGD3107 Saturday, 15 th November 2008 Multiplexers.

2. Function of Combinational Logic. Multiplexers:  A multiplexer (MUX) is a device that allows digital information from several sources to be routed onto a single line for transmission over that line to a common destination.  The basic multiplexer has several data-input lines and a single output line.  It also has data-select inputs. which permit digital data on anyone of the inputs to be switched to the output line.  Multiplexers are also known as data selectors.

3. Function of Combinational Logic. Multiplexers: A logic symbol for a 4-input multiplexer (MUX)  As shown in Figure 13.  Notice that there are two data-select lines because with two select bits.  Anyone of the four data-input lines can be selected. Fig. 13, Logic symbol for a 1-of-4 data selector/multiplexer.

4. Function of Combinational Logic. Multiplexers: The truth table for a 4-input multiplexer (MUX) Table 4, Data selection for a l-of- 4-multiplexer.

5. Function of Combinational Logic. Multiplexers: The Implementation for a 4-input multiplexer (MUX) Fig. 14, Logic diagram for a 4-input multiplexer.

6. Function of Combinational Logic. Multiplexers: THE 74LS151 8-INPUT DATA SELECTOR/MULTIPLEXER Fig. 15, Pin diagram and Logic symbol for the 74LS151 8 input data selector / multiplexer. The 74LS151 has eight data inputs (D 0 –D 7 ) and, therefore, three data-select or address input lines (S 0 -S 2 ), Three bits are required to select anyone of the eight data inputs (2 3 = 8).

7. Function of Combinational Logic. Multiplexers: Example 2: Use 74LS151, and any other logic necessary to multiplex 16 data lines onto a single data-output line.  An implementation of this system is shown in Figure 16.  Four bits are required to select one of 16 data inputs (2 4 = 16).  In this application the Enable input is used as the most significant data- select bit.  When the MSB in the data-select code is LOW, the left 74LS151 is enabled, and one of the data inputs (Do through D 7 ) is selected by the other three data-select bits.  When the data-select MSB is HIGH, the right 74LS151 is enabled, and one of the data inputs (D 8 through D 15 ) is selected.  The selected input data are then passed through to the negative-OR gate and onto the single output line. Solution:

8. Function of Combinational Logic. Multiplexers: Solution: Fig. 16, A 16-input multiplexer.

9. Applications: Function of Combinational Logic. Multiplexers: A 7-Segment Display Multiplexer