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SparkyNZ's avatar
SparkyNZ
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5 years ago

multiple drivers due to the non-tri-state driver

Can someone please help me with this error. Warning (13035): Inserted always-enabled tri-state buffer between "VGAController:vgaController|dataH" and its non-tri-state driver. Error (13076): The ...
SparkyNZ's avatar
SparkyNZ
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5 years ago

Well.. I may have resolved my issue. If I have, I don't think the error message was very helpful in this case. The error appears to be caused by this line, which neither mentions dataH or ioData:

iDataCopy = iData; // Caused by this

dataH = iDataCopy[ 15 : 8 ];

I know that ioData is connected to iData, so that's one part of the puzzle, but I still don't know why the assignment to dataH from iDataCopy would be a problem??

I've changed the code as follows so that iData is only connected to dataIncoming when the chipSelect is high or HiZ otherwise.

logic [15 : 0 ] dataIncoming = 0;
assign dataIncoming = ( chipSelect ) ? iData : 16'bZZZZZZZZZZZZZZZZ;
..
//iDataCopy = iData; // This will give "multiple drivers due to the non-tri-state driver" error
iDataCopy = dataIncoming;
dataH = iDataCopy[ 15 : 8 ];

So why did Quartus give me the error? Is is because the incoming iData/ioData wire was driving iDataCopy and another register in another module? If so, why does the error refer to dataH and not iDataCopy?

Update: No, the above didn't work either..

Error (13076): The node "VGAController:vgaController|dataH" has multiple drivers due to the conflicting nodes "dataBus[8]" and "SDRAMController8Bit:sdramController|ioData[8]"

Why do I have conflicting nodes? Is this because VGAController takes data from an input wire and SDRAMController uses an inout wire? The dataBus wire is declared as inout in my top module

Google has no results for "multiple drivers due to the conflicting nodes". I'm completely stumped.

  • SparkyNZ's avatar
    SparkyNZ
    Icon for Contributor rankContributor
    5 years ago

    I'm further confused again.. I now have a problem in my Top level module:

    // Shared buses
wire  [15 : 0 ] dataBus;
// Registers to be switched onto the bus
logic [15 : 0 ] dataRAM;

//bit[ 15:0 ] dataVal;
logic[ 15:0 ] dataVal;  // logic or bit? Made no difference
..
assign dataBus    = ( chipSelectRAM ) ? dataRAM    : 16'bZZZZZZZZZZZZZZZZ;
..
always_ff @( posedge clk  )
..
  dataVal       = dataBus;   // Error here

    Error (13076): The node "dataVal" has multiple drivers due to the non-tri-state driver "SDRAMController8Bit:sdramController|ioData[8]"

    dataBus is connected to sdramController's ioData wire

    dataRAM was being used for outgoing data.

    So I modified the code further, renaming dataRAM to dataOut and adding a dataIn and now it compiles:

    logic [15 : 0 ] dataOut;
logic [15 : 0 ] dataIn;

assign dataBus    = ( chipSelectRAM ) ? dataOut    : 16'bZZZZZZZZZZZZZZZZ;      // Do I need to include iSDRAMWriteRequest here??
assign dataIn     = ( chipSelectRAM ) ? dataBus    : 16'bZZZZZZZZZZZZZZZZ;      // Do I need to include ~iSDRAMWriteRequest here??

    Question: If using dataBus for incoming and outgoing data, do I always need to provide a separate register for incoming and outgoing as I have done above?