Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
8 years ago

Can't resolve multiple constant drivers

I have a process 


type StateType is (ST_IDLE, ST_WAIT_DONE, ST_START_RX_DATA, ST_RX_DATA0, ST_RX_DATA, ST_RX_REG_COM, ST_RX_REG_ADDR, ST_RX_REG_DATA, ST_TX_REG_COM,  ST_TX_REG_ADDR, ST_TX_REG_DATA, ST_TX_REG_DONE, ST_READ_STATUS_0, ST_READ_STATUS_1, ST_START_TX_DATA, ST_TX_DATA, ST_WAIT_USER_DONE);
signal State :StateType;
signal NextState :StateType;
mspi_mcp25625_interface: process (REG_CLK) 
begin 
    if (rising_edge(REG_CLK)) then
  
      case State is
  
        when ST_IDLE =>
        MSPI_WR_START_TRIG <= '0';
        MSPI_WR_DONE_CLR  <= '0';
        if (MCP25625_RX0BF='0' or MCP25625_RX1BF='0') then
            State <= ST_START_RX_DATA;
        end if;
      
    when ST_WAIT_DONE =>
        MSPI_WR_START_TRIG <= '0';
        MSPI_WR_DONE_CLR <= '0';
            if (MSPI_WR_DONE = '1') then 
          MSPI_WR_DONE_CLR <= '1';
          if (NextState = ST_RX_DATA) then
             if (rx_byte_idx < DATA_LENGHT) then
                temp_rx_mailbox(rx_byte_idx) <= MSPI_RD_DATA; 
              rx_byte_idx := rx_byte_idx + 1; --index for next rx byte
--             else
--               rx_byte_idx := 0;
--             State <= ST_IDLE;
           end if; 
        elsif (NextState = ST_RX_REG_DATA) then
              mcp25625_reg_data <=  MSPI_RD_DATA;
              elsif (NextState =  ST_READ_STATUS_1) then
              mcp25625_status_reg <= MSPI_RD_DATA;  
          end if;
        State <= NextState;
      else   --timeout 
                timeout <= timeout + 1; 
              if (timeout >= X"FFFE") then
            timeout <= X"0000";
        State <= ST_IDLE;
            end if;     
      end if;  
    
            ---------------------------------------RECEIVE MAILBOX FROM MCP25625-------------------------
    
        when ST_START_RX_DATA =>      --start to receive a mailbox
     if (MCP25625_RX0BF='0') then
      MSPI_WR_DATA <= X"90";  --Receive Buffer 0, Start at RXB0SIDH (0x61) 
     elsif (MCP25625_RX1BF='0') then
      MSPI_WR_DATA <= X"94";  --Receive Buffer 1, Start at RXB1SIDH (0x71)
     end if;
     MSPI_CS <= '0';            --chip select low
     MSPI_WR_START_TRIG <= '1'; --send a byte
     NextState <= ST_RX_DATA0;
     State <= ST_WAIT_DONE;
     
    when ST_RX_DATA0 =>           --skip first byte - it was a command
          MSPI_WR_DONE_CLR <= '0';
          State <= ST_RX_DATA;
      
    when ST_RX_DATA =>                 --receive a mailbox
        MSPI_WR_DONE_CLR <= '0'; 
        if (rx_byte_idx < DATA_LENGHT) then
            MSPI_WR_DATA <= X"00";     --load dummy byte
            MSPI_WR_START_TRIG <= '1'; --send a byte
          NextState <= ST_RX_DATA;
          State <= ST_WAIT_DONE;   
        else                           --13 bytes received
              MSPI_CS <= '1';            --chip select high 
            rx_byte_idx := 0;
        --MCP25625_DATA_RDY <= '1';  --WHERE TO CLEAR?
        rx_data_ready <= '1';
          NextState <= ST_IDLE;
          State <= ST_IDLE;
          end if; 
 when others =>
        State <= ST_IDLE;
      end case; 
    end if;         
end process mspi_mcp25625_interface;

When I compile I get multiple errors :

Error (10028): Can't resolve multiple constant drivers for net "State.ST_IDLE"……

Error (10028): Can't resolve multiple constant drivers for net "State.ST_WAIT_DONE" …..

Error (10028): Can't resolve multiple constant drivers for net "State.ST_START_RX_DATA" …..

And so on.

But I use State only in this process.

12 Replies

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

    I get the feeling you dont - as this can only come about by driving state from multiple processes

    Please post the whole code.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    You haven't given us the full picture. There doesn't appear to be anything wrong with what you've posted...

    Cheers,

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

    This is the complete code

    As a standalone file it compiles without errors. The errors appear only if I make a component of the entity and map it.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    You have assigned it in two different processes:

    process @ line 127

    process @ line 201 : mspi_mcp25625_interface

    you also have a 3rd process (@ line 433) that is commented out that also assigns state.

    Took me 10s to find with the search function in a text editor....
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    I see. Thank you. I've missed it. I realy need to control the State from another proccess - what should I do?

    I also have RAM in my project and I need to read/wrte to it fom several processes - I realize I can't do it either.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    --- Quote Start ---

    I see. Thank you. I've missed it. I realy need to control the State from another proccess - what should I do?

    I also have RAM in my project and I need to read/wrte to it fom several processes - I realize I can't do it either.

    --- Quote End ---

    1) Send a signal from the other process to the state machine process.

    2) Build a memory arbitrator to decide who can access the ram at any given point.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    --- Quote Start ---

    1) Send a signal from the other process to the state machine process.

    2) Build a memory arbitrator to decide who can access the ram at any given point.

    --- Quote End ---

    I see. So if I want to change State from several processes I should send several different signals – each signal belongs to its process?

    If so - I can do the same for RAM?

    The problem is - I set a signal high, but how do I know when to set the signal low?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    The state machine needs to exist in a single process.

    You communicate with a process via signals.

    You can just have outputs from the state machines when something have finished etc, or just read the state of the state machine.

    It sounds like you're taking VHDL as a programming language. You may need to draw out your intended circuit BEFORE writing any VHDL. without knowing what circuit you want, you will not write the correct VHDL.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    One more thing 

    
when ST_WR_RAM =>	  
    ram_addr := to_integer(unsigned(addr_bus));
    ram_mem(ram_addr) <= REG_DATA1_IN;
					 
when ST_RD_RAM => 
    ram_addr := to_integer(unsigned(addr_bus));
    REG_DATA_OUT <= ram_mem(ram_addr);
				
when ST_RAM_TO_MCP25625  => 
    temp_ram_val <= ram_mem(ram_addr);

    I get - Error (10028): Can't resolve multiple constant drivers.

    If I comment out REG_DATA_OUT <= ram_mem(ram_addr); or temp_ram_val <= ram_mem(ram_addr); It compiles without errors.

    Why I can't write to different signals in the same process?