A combinational circuit has three inputs- y, and z-and three outputs R. The simplified Boolean functions for the circuit are: Decoder Implementation F = xz + x,y,z' Implement and test the combinational circuit, using a 74155 decoder IC and NAND gates external The block diagram of the decoder and its truth table are shown in Fig, 9.7 The 2415 can be connected as a dual 2 x 4 decoder or as a single 3 x 8 decoder. When a 3 x decoder is desired, inputs CI and C2, as well as inputs G1 and G2, must be connected together, as shown in the block diagram. The function of the circuit is similar to that illustrated in Fig. 4.18. G is the enable input and must be equal to 0 for proper opera tion. The eight outputs are labeled with symbols given in the data book.The 74155 use NAND gates,with the result that the selected output goes to 0 while all other outputs remain at 1. The implementation with the decoder is as shown in Fig, 4.21, except that the OR gates must be replaced with external NAND gates when the 74155 is used