Hardware Reference
In-Depth Information
1 //Module header:-----------------------------------------------
2 module car_alarm_with_chirps (
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input logic remt, sen, clk, rst,
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output logic siren);
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6 //Declarations:------------------------------------------------
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//FSM-related declarations:
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typedef enum logic [3:0] {disarmed, armed, alarm, chirp1,
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chirp2, chirp3, chirp4, chirp5, wait1, wait2} state;
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state pr_state, nx_state;
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//Timer-related declarations:
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const logic [23:0] chirpON = 15_000_000; //0.3s @fclk=50MHz
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const logic [23:0] chirpOFF = 15_000_000;
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logic [23:0] t, tmax; --range≥max(chirpON,chirpOFF)
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18 //Statements:--------------------------------------------------
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//Timer (using strategy #2):
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always_ff @(posedge clk, posedge rst)
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if (rst) t <= 0;
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else if (t < tmax) t <= t + 1;
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else t <= 0;
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//FSM state register:
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always_ff @(posedge clk, posedge rst)
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if (rst) pr_state <= disarmed;
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else pr_state <= nx_state;
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//FSM combinational logic:
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always_comb
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case (pr_state)
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disarmed: begin
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siren <= 1'b0;
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tmax <= 0;
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if (remt) nx_state <= chirp1;
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else nx_state <= disarmed;
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end
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chirp1: begin
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siren <= 1'b1;
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tmax <= chirpON-1;
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if (t==tmax) nx_state <= wait1;
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else nx_state <= chirp1;
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end
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wait1: begin
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siren <= 1'b0;
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tmax <= 0;
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if (~remt) nx_state <= armed;
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else nx_state <= wait1;
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end
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armed: begin
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siren <= 1'b0;
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tmax <= 0;
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if (sen) nx_state <= alarm;
