Design a circuit to detect signal toggling

Theoretically, the simplest way to detect whether a signal has changed is to directly compare the current value Value(T) with the last clock cycle value Value(T-1). Thus, we just need to delay/save the value from last clock cycle using one register.

// Design a Toggle Detector
module toggle_detector (input din, rst,
                        output toggle, rist, fall,
                        output reg dout
);

always @ (posedge clk or negedge rst)
    if (~rst)
        dout <= 1'b0;
    else
        dout <= din;

assign toggle = (din^dout); // toggled
assign rise = ~din & dout; // High -> Low
assign fall = din & ~dout; // Low -> High

endmodule

// Design a Toggle Detector

module toggle_detector (input din, rst,

output toggle, rist, fall,

output reg dout

);

always @ (posedge clk or negedge rst)

if (~rst)

dout <= 1'b0;

else

dout <= din;

assign toggle = (din^dout); // toggled

assign rise = ~din & dout; // High -> Low

assign fall = din & ~dout; // Low -> High

endmodule

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