Digital Electronics: Principles, Devices and Applications

Programmable Logic Devices 323indicate the power level, with ‘L’ and ‘Q’ respectively indicating low and quarter power levels and ablank representing full power.Example 9.4Table 9.4 shows the function table of a converter. Starting with the Boolean expressions for the fouroutputs (P, Q, R, S), minimize them using Karnaugh maps and then hardware-implement this converterwith a suitable PLD with PAL architecture.SolutionFrom the given function table, we can write the Boolean expressions for the four outputs as follows:P = ABCD+ ABCD + ABCD + ABCD + ABCD (9.13)Q = ABCD + ABCD (9.14)R = ABCD + ABCD + ABCD + ABCD+ ABCD + ABCD (9.15)S = ABCD+ ABCD + ABCD + ABCD (9.16)Karnaugh maps for the four outputs P,Q,R and S are respectively shown in Figs 9.21(a) to (d). Theminimized Boolean expressions are given by the equationsTable 9.4 Function table in example 9.4.A B C D P Q R S0 0 0 0 0 0 0 00 0 0 1 0 0 0 10 0 1 0 0 0 1 10 0 1 1 0 0 1 00 1 0 0 0 1 1 00 1 0 1 1 1 1 00 1 1 0 1 0 1 00 1 1 1 1 0 1 11 0 0 0 1 0 0 11 0 0 1 1 0 0 01 0 1 0 X X X X1 0 1 1 X X X X1 1 0 0 X X X X1 1 0 1 X X X X1 1 1 0 X X X X1 1 1 1 X X X X