数字电路英文版第十一单元.pptVIP

Moore state machine: The output depend only on the internal state and any inputs that are synchronized with the circuit. Counters are examples of the Moore type of state machine. Mealy state machine: The outputs are depend by both the internal state and by inputs that are not synchronized with the circuit. State_diagram QSTATE State A : if Y then B else H ; State B : if Y then C else A ; State C : if Y then D else B ; State D : if Y then E else C ; State E : if Y then F else D ; State F : if Y then G else E ; State G : if Y then H else F ; State H : if Y then A else G ; Test vectors is same as example 11-4. 61 §11.5 PLD SYSTEM IMPLEMENTATION In this section, a specific example is used to illustrate the use of the state diagrams and other entry methods to implement a complete system with PLDs using ABEL. The examples system is an elevator control for a two-floor building and uses two GAL16V8 devices. 62 The System State control logic GAL16V8 Display logic GAL16V8 LCK REQ1 REQ2 FLOOR2 FLOOR1 OPEN ARRIVE L1PB L1PB_ L2PB L2PB_ DOOR MOTION DIR Floor sensor switch Push_button inputs Push_button latch outputs 7-segment floor display Up arrow Down arrow 63 Output Variable State DOOR 0 = Open 1 = Close MOTION 0 = Wait 1 = Move DIR 0 = Up 1 = Down TABLE 11-3 64 Inputs to the State Control Logic CLK : The clock signal establishes the length of time that the door remains open. The period of the clock is 10s. REQ1 : Request for the elevator to come to the first floor. (outside of the door) REQ2 : Request for the elevator to come to the second floor. (outside of the door) 65 FLOOR2 : Instruction for the elevator to go to the second floor. (inside the elevator) FLOOR1 : Instruction for the elevator to go to the first floor. (inside the elevator) OPEN