スクィーズ動作を実現するには、状態遷移表を用いたほうが簡単かも知れません。
//------- ELK Test Bench ---------
`timescale 1ms/1us
module tb_elk;
reg RST_N;
reg CLK;
reg IN_DOT;
reg IN_DASH;
ELK ELK_0(.RST_N (RST_N),
.CLK (CLK) ,
.IN_DOT (IN_DOT) ,
.IN_DASH (IN_DASH) ,
.KEY_OUT (KEY_OUT) );
initial begin
CLK <= 1'b1;
forever begin
#10;
CLK <= ~CLK;
end
end
initial begin
RST_N <= 1'b0;
#50;
RST_N <= 1'b1;
#1100000;
$finish;
end
initial begin
IN_DOT <= 1'b1; #063;
IN_DOT <= 1'b0; #073;
IN_DOT <= 1'b1; #323;
IN_DOT <= 1'b0; #223;
IN_DOT <= 1'b1; #243;
IN_DOT <= 1'b0; #023;
IN_DOT <= 1'b1; #1000000;
end
initial begin
IN_DASH <= 1'b1; #183;
IN_DASH <= 1'b0; #123;
IN_DASH <= 1'b1; #223;
IN_DASH <= 1'b0; #023;
IN_DASH <= 1'b1; #260;
IN_DASH <= 1'b0; #300;
IN_DASH <= 1'b1; #1000000;
end
endmodule
module ELK(RST_N, CLK, IN_DOT, IN_DASH, KEY_OUT);
input RST_N;
input CLK;
input IN_DOT;
input IN_DASH;
output KEY_OUT;
reg KEY_OUT;
reg m_dot;
reg m_dash;
reg[2:0] r_state;
//--------- dot memory ---------------------
always @ (negedge IN_DOT or negedge RST_N) begin
if ( RST_N == 1'b0 ) begin
m_dot <= 1'b0;
end if ( IN_DOT == 1'b0) begin
m_dot <= 1'b1;
end
end
//--------- dash memory ---------------------
always @ (negedge IN_DASH or negedge RST_N) begin
if ( RST_N == 1'b0 ) begin
m_dash <= 1'b0;
end if ( IN_DASH == 1'b0) begin
m_dash <= 1'b1;
end
end
//--------- state output ---------------------
always @ (r_state) begin
case(r_state)
3'b000: begin KEY_OUT <= 1'b0; end
3'b001: begin KEY_OUT <= 1'b1; end
3'b010: begin KEY_OUT <= 1'b1; end
3'b011: begin KEY_OUT <= 1'b1; end
3'b100: begin KEY_OUT <= 1'b0; end
3'b101: begin KEY_OUT <= 1'b1; end
3'b110: begin KEY_OUT <= 1'b0; end
default:begin
end
endcase
end
//--------- state transition ---------------------
always @ (posedge CLK or negedge RST_N) begin
if ( RST_N == 1'b0 ) begin
r_state <= 3'b000;
end else
case (r_state)
3'b000:begin // idle
if(IN_DASH == 1'b0) begin
r_state <= 3'b001;
end else if(IN_DOT == 1'b0) begin
r_state <= 3'b101;
end
end
3'b001:begin // dash running 1
r_state <= 3'b010;
m_dash <= 1'b0;
end
3'b010:begin // dash running 2
r_state <= 3'b011;
end
3'b011:begin // dash running 3
r_state <= 3'b100;
end
3'b100:begin // dash running 4
if(IN_DOT == 1'b0 || m_dot == 1'b1) begin
r_state <= 3'b101;
m_dot <= 1'b0;
end else if(IN_DASH == 1'b0) begin
r_state <= 3'b001;
end else begin
r_state <= 3'b000;
end
end
3'b101:begin // dot running 1
r_state <= 3'b110;
m_dot <= 1'b0;
end
3'b110:begin // dot running 2
if(IN_DASH == 1'b0 || m_dash == 1'b1) begin
r_state <= 3'b001;
m_dash <= 1'b0;
end else if(IN_DOT == 1'b0) begin
r_state <= 3'b101;
end else begin
r_state <= 3'b000;
end
end
default:begin
end
endcase
end
endmodule
