Lecture 5 Key Locker using FPGA 2007/10/05 Prof. C.M. Kyung

2/17 Key Locker Design Using FPGA 1. GOAL is ~ (1) Understanding of FSM and Its Sequential Behaviors (2) Understanding of the Design Procedure for FSM (3) Design of the FSM for Key Locker and Implementation on FPGAs

3/17 Key Locker Design Using FPGA 2. Review of Sequential Logic Circuits (1) Sequential Systems - Having memory. - The current state is “held” in memory and the next state is computed based on the current state and the current inputs. - Clock orchestrates the sequence of events

4/17 Key Locker Design Using FPGA 2. Review of Sequential Logic Circuits (1) Basic Building Blocks for Sequential Systems - D Flip Flop - T Flip Flop

5/17 Key Locker Design Using FPGA 3. Design Procedure for State Machines (1) Description of SM - State diagram, SM chart, … (2) State Optimization - Elimination of redundant states, … (3) State Encoding - Gray, One-hot, Thermometer, … (4) Logic Minimization - K-MAP, Quine-Mckluskey Method, … In modern design flows, these are usually done easily with CAD tools

6/17 Key Locker Design Using FPGA 4. State Machine Design (1) State Graph, State Table

7/17 Key Locker Design Using FPGA 4. State Machine Design (2) No state machine optimization (3) State encoding

8/17 Key Locker Design Using FPGA 4. State Machine Design (4) Result of Logic Minimization

9/17 Key Locker Design Using FPGA 5. Practical Design of FSM (1) In good design, data path and control path are clearly separated

10/17 Key Locker Design Using FPGA (2) Example description of FSM in Verilog HDL

11/17 Key Locker Design Using FPGA (3) Timing Constraints for Sequential Logics - Set-up time (T su ) Input should be “set-up” early enough before the clocking event. - Hold time (T h ) Input should be “held” at least some time after the clocking event.

12/17 Key Locker Design Using FPGA (4) Synchronizations of External Inputs - Bouncing - In mechanical switching, any two metal contacts generate multiple signals as the contacts close or open. - This should be prohibited for properly working in the digital logic circuits.

13/17 Key Locker Design Using FPGA (5) De-bouncing Technique - RC De-bouncer - Flip-Flop Based De-bouncer - Software Based De-bouncer switch signal CLK

14/17 Key Locker Design Using FPGA 6. Problem statement (1) Key Locker System - Given the *XXXXX* as the password input, the electric locker will be open or not. - Illegal password input should be handled gracefully. - Design should be implemented and verified within EPLD.

15/17 Key Locker Design Using FPGA 6. Problem statement (2) Key-Pad Circuit

16/17 Key Locker Design Using FPGA 6. Problem statement (3) Finite State Machine for Key Locker - Input from key-pad should be de-bounced - For each input from the key-pad circuit, the internal state in the FSM should be transit properly. - Password checking including illegal password handling.

17/17 Key Locker Design Using FPGA 7. Experiment Requirements (1) Equipment - Breadboard - KeyLocker Machine - DC Power Supply (2) Component - Switch (3) TTL IC’s (2 input NAND gate) (Inverter) (2 input AND gate) (3 input NAND gate) - 74LS73 ( Dual J-K flip-flop ) - 74LS74 ( Dual D-Type flip-flop )

18/17 Key Locker Design Using FPGA 8. References (1) Textbook - Contemporary Logic Design- Katz - Fundamentals of Logic Design- Roth (2) 5 st Week T.A. (3) Lecture Homepage