Chapter 3 − Combinational Circuits Page 1 of 44 Contents Combinational Circuits | Chapter 3 - Combinational Circuits Page 1 of 44 Contents Combinational Analysis of Combinational Using a Truth Using a Boolean Synthesis of Combinational Technology Minimization of Combinational Karnaugh Don Tabulation Timing Hazards and Using BCD to 7-Segment Decoder VHDL for Combinational Structural BCD to 7-Segment Dataflow BCD to 7-Segment Behavioral BCD to 7-Segment Summary Digital Logic and Microprocessor Design with VHDL Last updated 6 16 2004 6 29 PM Chapter 3 - Combinational Circuits Page 2 of 44 Chapter 3 Combinational Circuits Control Inputs Data Inputs Control unit 1 ff 1 -ELJ- State Next- Memory state Logic register Output Logic K. . y P K. P Control Signals P K. I P register ALU 1 0 I Datapath _ 8 Status Signals 8 Control Outputs Data Outputs Digital Logic and Microprocessor Design with VHDL Last updated 6 16 2004 6 29 PM Chapter 3 - Combinational Circuits Page 3 of 44 Digital circuits regardless of whether they are part of the control unit or the datapath are classified as either one of two types combinational or sequential. Combinational circuits are the class of digital circuits where the outputs of the circuit are dependent only on the current inputs. They do not remember the history of past inputs and therefore do not require any memory elements. Sequential circuits on the other hand are circuits whose outputs are dependent on not only the current inputs but also on past inputs. Because of their dependency on past inputs sequential circuits must contain memory elements in order to remember the past input values. A large digital circuit however may contain both combinational circuits and sequential circuits. However regardless of whether it is a
