VGA - horizantal sync pulse generation

Altera_Forum · ‎09-17-2011

hey,

I am trying to generate horizantal sync pulse with FSM.

I write the next verilog code:

 
module horizantal_sync_pluse (
       clock,    //system clock
       reset,   //system reset
       sync_pulse   //horizantal sync pulse
       );
//State machine parameters
parameter Scan_Line=1'b0;
parameter Gen_Sync_Pulse=1'b1;
//----------------------------------
input clock;
input reset;
output sync_pulse;
reg sync_pulse;
reg  state;
reg  counter;
always@(posedge clock, negedge reset)
begin
 if (reset==0) 
 begin 
  state<=Gen_Sync_Pulse;
  sync_pulse<=1'b0;
 end begin
  case (state) 
   Gen_Sync_Pulse:
    if (counter==11'h00BC) begin //188
     counter<=counter+1'b1;
     state<=Gen_Sync_Pulse;
     sync_pulse<=1'b0;
    end else
    begin
     state<=Scan_Line;
    end
   Scan_Line:
    if (counter==11'h639) begin
     sync_pulse<=1'b1;
     counter<=counter+1'b1;
     state<=Scan_Line;
    end else
    begin
     state<=Gen_Sync_Pulse;
     counter<=0;
    end
    default:
     state<=Gen_Sync_Pulse;
     
   endcase
end
end
endmodule

after compilation I get Warning: Latch counter[0] has unsafe behavior

Warning: Ports D and ENA on the latch are fed by the same signal sync_pulse~5

This warning is on each bit of the counter.

why is it? how can I avoid it?

Thanks

Altera_Forum · ‎09-17-2011

I haven't done verilog for years but I think you got simple error,

if reset == 0

begin

.....

end

else begin // you should put else here

....

Altera_Forum · ‎09-18-2011

Thanks. it happens to me sometimes, skip on this or that word. very diffecult to find asuch mistake by myself.

Thanks again

Altera_Forum · ‎09-18-2011

Another question.

I would like define

parameter Scan_Line=1'b0;

parameter Gen_Sync_Pulse=1'b1;

But I don't want that it will be showed in block diagram as parameter to change.

please see atachment.

How can I do it?

Thanks

Altera_Forum · ‎09-18-2011

Well you can just not declare the unwanted parameters and use their assigned values directly in your code to replace their names.

Parameter is for helping code readability/updating only. At compile time they are replaced by its value.

Altera_Forum · ‎09-18-2011

--- Quote Start ---

I would like define

parameter Scan_Line=1'b0;

parameter Gen_Sync_Pulse=1'b1;

How can I do it?

--- Quote End ---

Try

localparam Scan_Line=1'b0;

localparam Gen_Sync_Pulse=1'b1;

Cheers,

Dave

Altera_Forum · ‎09-18-2011

Well Dave, I should add you to the list of My Gurus. So far only FvM and josyb managed to get there.

Regards

Altera_Forum · ‎09-18-2011

Hey Kaz,

--- Quote Start ---

I should add you to the list of My Gurus. So far only FvM and josyb managed to get there.

--- Quote End ---

You are too kind.

I just happened to see localparam used in some of the Altera Verilog :)

Cheers,

Dave