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Altera_Forum's avatar
Altera_Forum
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16 years ago

detect video Signal

hello, could someone explain me this following code? i have found it in a demo application but with no Comments. thank you

module sigdetect(

oTD_Stable,

iTD_VS,

iTD_HS,

iRST_N );

input iTD_VS;

input iTD_HS;

input iRST_N;

output oTD_Stable;

reg TD_Stable;

reg Pre_VS;

reg [7:0] Stable_Cont;

assign oTD_Stable = TD_Stable;

always@(posedge iTD_HS or negedge iRST_N)

begin

if(!iRST_N)

begin

TD_Stable <= 1'b0;

Stable_Cont <= 4'h0;

Pre_VS <= 1'b0;

end

else

begin

Pre_VS <= iTD_VS;

if(!iTD_VS)

Stable_Cont <= Stable_Cont+1'b1;

else

Stable_Cont <= 0;

if({Pre_VS,iTD_VS}==2'b01)

begin

if(Stable_Cont==9)

TD_Stable <= 1'b1;

else

TD_Stable <= 1'b0;

end

end

end

6 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    --- Quote Start ---

    i cannot find this info that the V-blank is 9 horizontal sync pulses, can you give me more details...thanks

    --- Quote End ---

    It's depend on video signal. Different video signal have different parameter. The exactly 9 pulses looks very strange. Usually for video signal specified duration of V-blank, H-blank. And not exactly. You can find parameters for PAL or SECAM or VGA.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    --- Quote Start ---

    It's you video signal parameter. You V-blank duration is 9 horizontal sync pulses.

    --- Quote End ---

    i cannot find this info that the V-blank is 9 horizontal sync pulses, can you give me more details...thanks
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    --- Quote Start ---

    thank you for your Answer, aber i can't understand why 9 pulse is using

    --- Quote End ---

    It's you video signal parameter. You V-blank duration is 9 horizontal sync pulses.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    --- Quote Start ---

    hello, could someone explain me this following code? i have found it in a demo application but with no Comments. thank you

    module sigdetect(

    oTD_Stable,

    iTD_VS,

    iTD_HS,

    iRST_N );

    input iTD_VS;

    input iTD_HS;

    input iRST_N;

    output oTD_Stable;

    reg TD_Stable;

    reg Pre_VS;

    reg [7:0] Stable_Cont;

    assign oTD_Stable = TD_Stable;

    always@(posedge iTD_HS or negedge iRST_N)

    begin

    if(!iRST_N)

    begin

    TD_Stable <= 1'b0;

    Stable_Cont <= 4'h0;

    Pre_VS <= 1'b0;

    end

    else

    begin

    Pre_VS <= iTD_VS;

    if(!iTD_VS)

    Stable_Cont <= Stable_Cont+1'b1;

    else

    Stable_Cont <= 0;

    if({Pre_VS,iTD_VS}==2'b01)

    begin

    if(Stable_Cont==9)

    TD_Stable <= 1'b1;

    else

    TD_Stable <= 1'b0;

    end

    end

    end

    --- Quote End --- 

    module sigdetect (oTD_Stable, iTD_VS, iTD_HS, iRST_N);
input iTD_VS;
input iTD_HS;
input iRST_N;
output oTD_Stable;
reg TD_Stable;
reg Pre_VS;
reg Stable_Cont;
assign oTD_Stable = TD_Stable;
always @ (posedge iTD_HS or negedge iRST_N) 
  begin if (!iRST_N)
    begin //all reset
    TD_Stable <= 1 'b0;
    Stable_Cont <= 4' h0;
    Pre_VS <= 1 'b0;
    end
  else
   begin //this is for each horisontal syno impulse 
     Pre_VS <= iTD_VS;
     if(!iTD_VS)Stable_Cont <= Stable_Cont+1' b1; // blank time. Old frame is finish. But new frame is not begun. count HS singal pulses during blank time. 
     else Stable_Cont <= 0;// draw frame. do nothing 
     if ({Pre_VS, iTD_VS} == 2 'b01)// new frame is begin. 
     begin
       if(Stable_Cont==9) TD_Stable <= 1' b1; // if during blank time been 9 pulses HS the signal is stable. 
       else TD_Stable <= 1 'b0; // signal not stable. 
     end
   end
end

    blank time os "back moving beam". I don't know how to in english.