ТЕМА: Статика

module PushButton_Debouncer(pulse, clk, kpulse, kclr, reset);
output pulse;
input  clk;         // "clk" is the clock
input  kpulse;		 // Key start one pulse
input	 kclr;			 // Clr puls automate
input  reset;

reg Tpre, Tpost;

assign pulse = (!Tpre) ^ Tpost;
wire write = ~((!Tpre)&kclr);

always @(posedge clk or negedge reset) begin
 if(!reset)
	 {Tpost, Tpre} <= 2'b01;
 else begin	 
    if(write == 1'b1) Tpre <= kpulse;
	 Tpost <= (!Tpre)&(kclr);
 end	 
end


endmodule

module PushButton_Debouncer(clk, PB, PB_state, PB_up, PB_down, reset);
input clk;         // "clk" is the clock
input PB;          // "PB" is the glitched, asynchronous, active low push-button signal
input reset;

output PB_state;   // 1 while the push-button is active (down)
output PB_down;    // 1 when the push-button goes down (just pushed)
output PB_up;      // 1 when the push-button goes up (just released)

// First use two flipflops to synchronize the PB signal the "clk" clock domain
reg PB_sync_0;  always @(posedge clk) PB_sync_0 <= ~PB;  // invert PB to make PB_sync_0 active high
reg PB_sync_1;  always @(posedge clk) PB_sync_1 <= PB_sync_0;

// Next declare a 16-bits counter
reg [15:0] PB_cnt;

// When the push-button is pushed or released, we increment the counter
// The counter has to be maxed out before we decide that the push-button state has changed

reg PB_state;  // state of the push-button (0 when up, 1 when down)
wire PB_idle = (PB_state==PB_sync_1);
wire PB_cnt_max = &PB_cnt;	// true when all bits of PB_cnt are 1's

//always@(posedge clk or negedge reset) if(!reset) PB_state <= 0;

always @(posedge clk or negedge reset) begin
//if(PB_idle)
//    PB_cnt <= 0;  // nothing's going on
//else
//begin
 if(!reset)
	 {PB_cnt, PB_state} <= 0;
 else begin	 
    PB_cnt <= (PB_idle)? 16'd0 : PB_cnt + 1'b1;  // something's going on, increment the counter
    if(PB_cnt_max) PB_state <= !PB_state;  // if the counter is maxed out, PB changed!
 end	 
end

wire PB_down = ~PB_state & ~PB_idle & PB_cnt_max;  // true for one clock cycle when we detect that PB went down
wire PB_up   =  PB_state & ~PB_idle & PB_cnt_max;  // true for one clock cycle when we detect that PB went up

endmodule