我写了个串口接收的程序，但是仿真的时候没有波形，下到片子里也没有反应，哪位高手给指点一下！ module onlyjie (clk,rst,rxd,rxd_buf);
input clk,rst,rxd;
output rxd_buf;
reg [15:0] div_reg;
reg div_baud;
reg [2:0] div8_rec_reg;
reg recstart;
reg clkbaud_rec;
reg [7:0] rxd_buf;
reg rec_reg1;
reg rec_reg2;
reg [2:0] state_rec0;
reg recstart_tmp;
parameter div_par=16'h41; //是波特率为38400的八倍分频；
always @ (posedge clk, negedge rst)
begin
if (!rst)
div_reg<=0;
else
begin
if (div_reg==div_par-1) div_reg<=0;
else
div_reg<=div_reg+1;
end
end
always @ (posedge clk, negedge rst)
begin
if (!rst)
div_baud<=0;
else
begin
if (div_reg==div_par-1)
div_baud<=~div_baud;
end
end
always @ (posedge div_baud, negedge rst)
begin
if (!rst)
div8_rec_reg<=0;
else if (recstart)
div8_rec_reg<=div8_rec_reg+1;
end
always @ (div8_rec_reg)
begin
if (div8_rec_reg==7)
clkbaud_rec=1;
else clkbaud_rec=0;
end
always @ (posedge div_baud,negedge rst)
begin
if (!rst)
begin
rec_reg1<=0;
rec_reg2<=0;
rxd_buf<=0;
state_rec0<=0;
recstart<=0;
recstart_tmp<=0;
end
else
begin
rec_reg1<=rxd;
rec_reg2<=rec_reg1;
if (state_rec0==0)
begin
if (recstart_tmp==1)
begin
recstart_tmp<=0;
recstart<=1;
state_rec0<=state_rec0+1;
end
else
if(!rec_reg1&&rec_reg2)
recstart_tmp<=1;
end
else if (state_rec0<=1&&state_rec0>=8)
begin
if (clkbaud_rec)
begin
rxd_buf[7]<=rec_reg2;
rxd_buf[6:0]<=rxd_buf[7:1];
state_rec0<=state_rec0+1;
end
end
else if (state_rec0==9)
begin
if (clkbaud_rec)
begin
state_rec0<=0;
recstart<=0;
end
end
end
end
endmodule
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