- 3 A Combination Lock Is A Kind Of Sequence Recognizer We Want To Build An Electronic Combination Lock Which Has One Lo 1 (95.71 KiB) Viewed 14 times
#3 A combination lock is a kind of sequence recognizer. We want to build an electronic combination lock which has one Lock (L) pushbutton and ten others for decimal digits 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. When a digit button is pushed it produces a signal 1: X, is 1, i being the number and others produce 0's. In the circuit, as a digit button is pushed it produces an input clocking signal C and at the rising edge the memory (flip-flops) latches the input. The L button produces an asynchronous Reset signal which brings the device to the initial state S, and locks. Unlocking occurs when the output signal U becomes 1 after a correct sequence of four digits being pressed (and released, one at a time). The 4 digits to unlock is stored in components: A B C D and have been set to some sequence, e.g., 7314, 9284, 0765, ... (can be anything). The circuit altogether has input X, lock L, clock C, output U, the secret digits (A B C D) and a set of flip-flops for memory state. (a) Design a Moore-model state-transition diagram. (b) Lay out the truth table. (c) Draw K-maps. (d) Compact Boolean equations. (e) Draw the gate-logic schema.