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Error: Line 74. Signal key_state has a multi source.

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nakshathra

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The following code results the error: Line 74. Signal key_state has a multi-source.
The code is written for a keypad scanner.
I cannot make out why "key_state" turned out to be multi source signal.

Please help!!!!!!!!!!!!!!

-- Thanks in Advance! :)
Code: 
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use IEEE.STD_LOGIC_arith.ALL;
use IEEE.STD_LOGIC_unsigned.ALL;


entity keypad is
  port (
    clk       : in  std_logic;
	 reset: in std_logic;
  key_pulse : out std_logic;
    key_code  : out std_logic_vector(3 downto 0);

    key_col : in  std_logic_vector(3 downto 0);
    key_row : out std_logic_vector(3 downto 0)
    );
end keypad;

architecture rtl of keypad is

  -- state machine states
  type KEY_STATES is (pulse_row_1, read_row_1, pulse_row_2, read_row_2,
                      pulse_row_3, read_row_3, pulse_row_4, read_row_4);

  signal key_state     : KEY_STATES                   ;
  signal clkcntr       : std_logic_vector(15 downto 0)        := (others=>'0');
  signal state_inc     : std_logic                    := '0';
  signal scan_complete : std_logic                    := '0';
  signal key_read      : std_logic_vector(3 downto 0) := (others => '0');
  signal keyread_sreg3 : std_logic_vector(3 downto 0) := (others => '0');
  signal keyread_sreg2 : std_logic_vector(3 downto 0) := (others => '0');
  signal keyread_sreg1 : std_logic_vector(3 downto 0) := (others => '0');
  signal keyread_sreg0 : std_logic_vector(3 downto 0) := (others => '0');

begin

  clkdiv : process (clk,reset)
  begin
	if reset = '1' then key_state<=pulse_row_1;             key_code  <= (others => '0');

    elsif clk' event and clk = '1' then     -- rising clock edge

      -- default
      state_inc <= '0';

      -- pulse state_inc signal every 50,000 clock cycles
      clkcntr <= clkcntr + 1;
      if clkcntr = X"C350" then
        clkcntr   <= (others => '0');
        state_inc <= '1';
      end if;
      
    end if;
  end process clkdiv;

  -- key scanner state machine
  -- output pulse on each key row and check for keypress
  key_scanner_sm : process (clk,reset)
  begin  -- process key_scanner
    if (clk' event and clk = '1' and reset = '0') then

      if state_inc = '1' then

        -- reset scan_complete
        scan_complete <= '0';

        case key_state is

          when pulse_row_1 =>
            key_row   <= "0111";
          key_state <= read_row_1;

          when read_row_1 =>
            case key_col is
              when "0111" => key_code <= "0001";  -- 1
              when "1011" => key_code <= "0010";  -- 2
              when "1101" => key_code <= "0011";  -- 3
              when "1110" => key_code <= "0000";  -- A
              when others => null;
            end case;
            key_state <= pulse_row_2;

          when pulse_row_2 =>
            key_row   <= "1011";
            key_state <= read_row_2;

          when read_row_2 =>
            case key_col is
              when "0111" => key_code <= "0100";  -- 4
              when "1011" => key_code <= "0101";  -- 5
              when "1101" => key_code <= "0110";  -- 6
              when "1110" => key_code <= "0000";  -- B
              when others => null;
            end case;
            key_state <= pulse_row_3;

          when pulse_row_3 =>
            key_row   <= "1101";
            key_state <= read_row_3;
            
          when read_row_3 =>
            case key_col is
              when "0111" => key_code <= "0111";  -- 7
              when "1011" => key_code <= "1000";  -- 8
              when "1101" => key_code <= "1001";  -- 9
              when "1110" => key_code <= "0000";  -- C
              when others => null;
            end case;
            key_state <= pulse_row_4;
            

          when pulse_row_4 =>
            key_row   <= "1110";
            key_state <= read_row_4;

          when read_row_4 =>
            case key_col is
              when "0111" => key_code <= "1111";  -- *
              when "1011" => key_code <= "0000";  -- 0
              when "1101" => key_code <= "1111";  -- #
              when "1110" => key_code <= "1111";  -- D
              when others => null;
            end case;
            key_state     <= pulse_row_1;
            scan_complete <= '1';

          when others => null;
        end case;

      end if;
    end if;
  end process key_scanner_sm;


  debounce : process (clk)
  begin
    if clk' event and clk = '1' then

      -- reset key_pulse
      key_pulse <= '0';

      if scan_complete = '1' then

        -- shift in key_read
        keyread_sreg3 <= key_read;
        keyread_sreg2 <= keyread_sreg3;
        keyread_sreg1 <= keyread_sreg2;
        keyread_sreg0 <= keyread_sreg1;

        -- vaild key press is a cycle of no keypress followed by 3 cycles of
        -- detecting the same key pressed
        if keyread_sreg3 = keyread_sreg2 and
          keyread_sreg2 = keyread_sreg1 and
          keyread_sreg1 /= keyread_sreg0 and
          keyread_sreg0 = X"0" then
          key_pulse <= '1';
          key_code  <= keyread_sreg3;
			           

        end if;
        
      end if;
    end if;
  end process debounce;

  
end rtl;
 
Last edited:

you assing key_state in the clkdiv process and the key_scanner_sm. You can only assing it in a single process.
 

I made few changes to it, yet getting this error:
ERROR:Xst:528 - Multi-source in Unit <keypad> on signal <N0>; this signal is connected to multiple drivers.

this time, which can be the signal that has multiple drivers?


Code: 
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use IEEE.STD_LOGIC_arith.ALL;
use IEEE.STD_LOGIC_unsigned.ALL;


entity keypad is
  port (
    clk       : in  std_logic;
	 reset: in std_logic;
  key_pulse : out std_logic;
    key_code  : out std_logic_vector(3 downto 0);

    key_col : in  std_logic_vector(3 downto 0);
    key_row : out std_logic_vector(3 downto 0)
    );
end keypad;

architecture rtl of keypad is

  -- state machine states
  type KEY_STATES is (pulse_row_1, read_row_1, pulse_row_2, read_row_2,
                      pulse_row_3, read_row_3, pulse_row_4, read_row_4);

  signal key_state     : KEY_STATES                   ;
  signal clkcntr       : std_logic_vector(15 downto 0)        := (others=>'0');
  signal state_inc     : std_logic                    := '0';
  signal scan_complete : std_logic                    := '0';
  signal key_read      : std_logic_vector(3 downto 0) := (others => '0');
  signal keyread_sreg3 : std_logic_vector(3 downto 0) := (others => '0');
  signal keyread_sreg2 : std_logic_vector(3 downto 0) := (others => '0');
  signal keyread_sreg1 : std_logic_vector(3 downto 0) := (others => '0');
  signal keyread_sreg0 : std_logic_vector(3 downto 0) := (others => '0');

begin

  clkdiv : process (clk,reset)
  begin

  if clk' event and clk = '1' then     -- rising clock edge

      -- default
      state_inc <= '0';

      -- pulse state_inc signal every 50,000 clock cycles
      clkcntr <= clkcntr + 1;
      if clkcntr = X"C350" then
        clkcntr   <= (others => '0');
        state_inc <= '1';
      end if;
      
 else null;   end if;
  end process clkdiv;

  -- key scanner state machine
  -- output pulse on each key row and check for keypress
  key_scanner_sm : process (clk,reset)
  begin  -- process key_scanner
  if(reset = '1') then key_code  <= (others => '0');    key_state <= pulse_row_1 ;
    elsif (clk' event and clk = '1' and reset = '0') then

      if state_inc = '1' then

        -- reset scan_complete
        scan_complete <= '0';

        case key_state is

          when pulse_row_1 =>
            key_row   <= "0111";
          key_state <= read_row_1;

          when read_row_1 =>
            case key_col is
              when "0111" => key_code <= "0001";  -- 1
              when "1011" => key_code <= "0010";  -- 2
              when "1101" => key_code <= "0011";  -- 3
              when "1110" => key_code <= "0000";  -- A
              when others => null;
            end case;
            key_state <= pulse_row_2;

          when pulse_row_2 =>
            key_row   <= "1011";
            key_state <= read_row_2;

          when read_row_2 =>
            case key_col is
              when "0111" => key_code <= "0100";  -- 4
              when "1011" => key_code <= "0101";  -- 5
              when "1101" => key_code <= "0110";  -- 6
              when "1110" => key_code <= "0000";  -- B
              when others => null;
            end case;
            key_state <= pulse_row_3;

          when pulse_row_3 =>
            key_row   <= "1101";
            key_state <= read_row_3;
            
          when read_row_3 =>
            case key_col is
              when "0111" => key_code <= "0111";  -- 7
              when "1011" => key_code <= "1000";  -- 8
              when "1101" => key_code <= "1001";  -- 9
              when "1110" => key_code <= "0000";  -- C
              when others => null;
            end case;
            key_state <= pulse_row_4;
            

          when pulse_row_4 =>
            key_row   <= "1110";
            key_state <= read_row_4;

          when read_row_4 =>
            case key_col is
              when "0111" => key_code <= "1111";  -- *
              when "1011" => key_code <= "0000";  -- 0
              when "1101" => key_code <= "1111";  -- #
              when "1110" => key_code <= "1111";  -- D
              when others => null;
            end case;
            key_state     <= pulse_row_1;
            scan_complete <= '1';

          when others => null;
        end case;

      end if;
    end if;
  end process key_scanner_sm;


  debounce : process (clk)
  begin
    if clk' event and clk = '1' then

      -- reset key_pulse
      key_pulse <= '0';

      if scan_complete = '1' then

        -- shift in key_read
        keyread_sreg3 <= key_read;
        keyread_sreg2 <= keyread_sreg3;
        keyread_sreg1 <= keyread_sreg2;
        keyread_sreg0 <= keyread_sreg1;

        -- vaild key press is a cycle of no keypress followed by 3 cycles of
        -- detecting the same key pressed
        if keyread_sreg3 = keyread_sreg2 and
          keyread_sreg2 = keyread_sreg1 and
          keyread_sreg1 /= keyread_sreg0 and
          keyread_sreg0 = X"0" then
          key_pulse <= '1';
          key_code  <= keyread_sreg3;
			           

        end if;
        
      end if;
    end if;
  end process debounce;

  
end rtl;
 

First of all, you have clashing libraries - numeric_std clashes with std_logic_arith. You should remove the non-standard std_logic_arith library (std_logic_unsigned is also non-standard, but it doesnt clash with anything).

As for your error: it does not refer to the code you posted.
 

I have no idea of d above error, but I somehow managed to make the code error free...
--Thanks a ton! :)
 

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