Thanks to Alvin A. and Hauke D.
I used a variable and it worked.
I will surely remember that it is not a C/pascal program but a circuit
description.

<meralonurlu@gmail.com> wrote in message
news:74798b96-6f57-4afd-8b29-2374fd04eb6c@t54g2000hsg.googlegroups.com...
> Xilinx ISE 9.2 and ISE 10.1
> I wanted to design a simple correlator which correlates a 15 bit
> sequence with another sequence of 15 bytes (8 bit signed values =
> Sample below). I needed to zero the summation result after 15 samples,
> so I did. But compiler didn't. There is no warning but even the
> simulator does not seem to notice ACC <= x"000000"; line. I do not see
> a reset input for the inferred updown accumulator in the RTL schematic
> either. But I see an unconnected D(L:R) input on accumulator.
> I see that, from the simulator outputs, Corr<=ACC; line is synthesized
> and working ok, though.
> What am I missing. Thanks for help to the beginner.
> Additional question (bonus? :-( ) : Waveform editor does not accept
> -100 for a 8-bit signed decimal signal but displays -28 instead. When
> I enter binary 10011100 which corresponds to -100 and display the
> values in decimal it interestingly displays -100. Does it mean -28
> equals to -100 somehow?
>
> architecture Rec of Rec is
>   constant PN : BIT_VECTOR (14 downto 0) := "000100110101111";
>   signal ACC  : SIGNED (23 downto 0) := x"000000";
>   signal cntr : integer range 0 to 14 := 0;
> begin
>   process(clk) begin
>     if(clk'event and clk='1') then
>       if(cntr=0) then
>         Corr <= ACC;
>         ACC <= x"000000";  -- Problematic line is this one
>       end if;
>       if(PN(cntr)='1') then
>         ACC <= ACC + Sample;
>       else
>         ACC <= ACC - Sample;
>       end if;
>       if(cntr=14) then
>         cntr <= 0;
>       else
>         cntr <= cntr +1;
>       end if;
>     end if;
>   end process;
> end Rec;

The clearing of the ACC will most likely be cancelled by the RN(cntr) = '1'
IF-block. This block should have been made dependend on the first condition:

       if(cntr=0) then
         Corr <= ACC;
         ACC <= x"000000";
       elsif(PN(cntr)='1') then
         ACC <= ACC + Sample;
       else
         ACC <= ACC - Sample;
       end if;

Regards,
Alvin.

Hi,

In the if-else immediately following your reset of ACC, you assign to
ACC again, overriding any previous assignment. Depending on the
intended behavior of your circuit you could switch to using variables
or reorganize your if's in a way that ACC is assigned only once.

Regards,
-- Hauke D


On Jun 28, 6:57=A0pm, meralonu...@gmail.com wrote:
> Xilinx ISE 9.2 and ISE 10.1
> I wanted to design a simple correlator which correlates a 15 bit
> sequence with another sequence of 15 bytes (8 bit signed values =3D
> Sample below). I needed to zero the summation result after 15 samples,
> so I did. But compiler didn't. There is no warning but even the
> simulator does not seem to notice ACC <=3D x"000000"; line. I do not see
> a reset input for the inferred updown accumulator in the RTL schematic
> either. But I see an unconnected D(L:R) input on accumulator.
> I see that, from the simulator outputs, Corr<=3DACC; line is synthesized
> and working ok, though.
> What am I missing. Thanks for help to the beginner.
> Additional question (bonus? :-( ) : Waveform editor does not accept
> -100 for a 8-bit signed decimal signal but displays -28 instead. When
> I enter binary 10011100 which corresponds to -100 and display the
> values in decimal it interestingly displays -100. Does it mean -28
> equals to -100 somehow?
>
> architecture Rec of Rec is
> =A0 constant PN : BIT_VECTOR (14 downto 0) :=3D "000100110101111";
> =A0 signal ACC =A0: SIGNED (23 downto 0) :=3D x"000000";
> =A0 signal cntr : integer range 0 to 14 :=3D 0;
> begin
> =A0 process(clk) begin
> =A0 =A0 if(clk'event and clk=3D'1') then
> =A0 =A0 =A0 if(cntr=3D0) then
> =A0 =A0 =A0 =A0 Corr <=3D ACC;
> =A0 =A0 =A0 =A0 ACC <=3D x"000000"; =A0-- Problematic line is this one
> =A0 =A0 =A0 end if;
> =A0 =A0 =A0 if(PN(cntr)=3D'1') then
> =A0 =A0 =A0 =A0 ACC <=3D ACC + Sample;
> =A0 =A0 =A0 else
> =A0 =A0 =A0 =A0 ACC <=3D ACC - Sample;
> =A0 =A0 =A0 end if;
> =A0 =A0 =A0 if(cntr=3D14) then
> =A0 =A0 =A0 =A0 cntr <=3D 0;
> =A0 =A0 =A0 else
> =A0 =A0 =A0 =A0 cntr <=3D cntr +1;
> =A0 =A0 =A0 end if;
> =A0 =A0 end if;
> =A0 end process;
> end Rec;

Xilinx ISE 9.2 and ISE 10.1
I wanted to design a simple correlator which correlates a 15 bit
sequence with another sequence of 15 bytes (8 bit signed values =
Sample below). I needed to zero the summation result after 15 samples,
so I did. But compiler didn't. There is no warning but even the
simulator does not seem to notice ACC <= x"000000"; line. I do not see
a reset input for the inferred updown accumulator in the RTL schematic
either. But I see an unconnected D(L:R) input on accumulator.
I see that, from the simulator outputs, Corr<=ACC; line is synthesized
and working ok, though.
What am I missing. Thanks for help to the beginner.
Additional question (bonus? :-( ) : Waveform editor does not accept
-100 for a 8-bit signed decimal signal but displays -28 instead. When
I enter binary 10011100 which corresponds to -100 and display the
values in decimal it interestingly displays -100. Does it mean -28
equals to -100 somehow?

architecture Rec of Rec is
  constant PN : BIT_VECTOR (14 downto 0) := "000100110101111";
  signal ACC  : SIGNED (23 downto 0) := x"000000";
  signal cntr : integer range 0 to 14 := 0;
begin
  process(clk) begin
    if(clk'event and clk='1') then
      if(cntr=0) then
        Corr <= ACC;
        ACC <= x"000000";  -- Problematic line is this one
      end if;
      if(PN(cntr)='1') then
        ACC <= ACC + Sample;
      else
        ACC <= ACC - Sample;
      end if;
      if(cntr=14) then
        cntr <= 0;
      else
        cntr <= cntr +1;
      end if;
    end if;
  end process;
end Rec;