baud rate transmitter program

baud rate transmitter program

module baudtransmitter(bclk,sysclk,rst,tdre,loadtdr,dbus,settdre,txd);

input bclk,sysclk,rst,tdre,loadtdr;

input [7:0]dbus;

output settdre,txd;

parameter idle=2'b00,synch=2'b01,tdata=2'b10;

reg [8:0]tsr;

reg [7:0]tdr;

reg [3:0]bct;

reg [1:0] state, nextstate;

reg inc, clr,loadtsr,shfttsr,start ,bclkdelayed;

wire bclkrising;

assign txd=tsr[0];

assign settdre=loadtsr;

assign bclkrising = bclk & (! bclkdelayed);

always@(state,tdre,bct,bclkrising)

begin

inc=1'b0; clr=1'b0; loadtsr=1'b0; shfttsr=1'b0; start=1'b0;

case(state)

idle: if(tdre==1'b0)

begin

loadtsr=1'b1;

nextstate=synch;

end

else nextstate=idle;

synch: if( bclkrising==1'b1 ) begin

start=1'b1;nextstate=tdata;

end

else nextstate=synch;

tdata: if( bclkrising==1'b0 ) nextstate=tdata;

else if(bct != 4'b1001)begin shfttsr=1'b1; inc=1'b1; nextstate=tdata; end

else begin clr=1'b1; nextstate=idle;end

endcase

end

always@( posedge sysclk or negedge rst)

begin

if(!rst)

begin

tsr=8'b11111111; state=idle; bct=1'b0; bclkdelayed=1'b0;

end

else

begin

state=nextstate;

if(clr==1'b1) bct=4'b0000;

else if (inc==1'b1) bct=bct+4'b0001;

if(loadtdr==1'b1) tdr=dbus;

if(loadtsr==1'b1) tsr={tdr,1'b1};

if(start==1'b1) tsr[0]=1'b0;

if(shfttsr==1'b1) tsr={1'b1 , tsr[8:1]};

bclkdelayed=bclk;

end

end

endmodule