90. -- Program X=(AC+(BC’)’+D)’+((BC)’)’=(A’+C’)(BC’)D’+BC -- =A’BC’D’+BC’D’+BC=(A’+1)BC’D’+BC = BC’D’+BC entity alogicft is port(B, C, D: in bit; X: out bit); end entity alogicft; architecture expaft of alogicft is begin X<= (B and not C and not D) or (B and C); end architecture expaft;
91. Levels of Abstraction for sequential logic circuits VHDL (1) Behavioral approach : state diagram or truth table (2) Data flow approach : Boolean expression or function (3) Structure approach : logic diagram or schematic describing logic function
94. Figure 4-59 Karnaugh map minimization of the segment- a logic expression.
95. Figure 4-60 The minimum logic implementation for segment a of the 7-segment display.
96. -- Program 7-segment driver entity sevensegdrv is port(A, B, C, D: in bit; a,b,c,d,e,f,g: out bit); end entity sevensegdrv; architecture segment of sevensegdrv is begin a<= B or D or (A and C) or (not A and not C); -- B +D+AC+A’C’ • • • • • • • • • g<= A or B and C’ or not B and C or C and not D; -- A+BC’+B’C+CD’ end architecture segment; VHDL for 7-Segment Driver
97.
98. The relationship between a single variable X, its complement X , and the binary constants 0 and 1