[VHDL] Xilinx Multi-source error

  • Thread starter dduardo
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In summary, there is an issue with connecting the output signals of the compression and decompression modules. This is due to the presence of tristate buffers and the way the signals are defined and driven. More information is needed to properly address the problem.
  • #1
dduardo
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Code:
ERROR:Xst:528 - Multi-source in Unit <codec> on signal <OP>
Sources are: 
   Output signal of FDC instance <compression/OP>
   Output signal of FDC instance <decompression/OP>

There are tristate buffers at the outputs of both the compression and decompression modules. Therefore if the compression is outputing, the decompression will be high impedance and vice versa. The problem is that Xilinx doesn't like how I'm doing it. How can I go about connecting the two outputs together?
 
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  • #2
I suspect that the main reason that no one has responded to this question is that, you haven't given enough information. For example, how are your signals defined? If they are defined improperly the reply could easily happen. Also, the nature of your output drive logic could be a problem. To tackle the problem all the info on it is needed>

KM
 
  • #3


It seems like the issue here is that both the compression and decompression modules are trying to drive the same signal <OP> at the same time, which is causing a multi-source error. This is because Xilinx does not support multiple drivers on the same signal. To resolve this, you can use a multiplexer to select which output signal to drive <OP> based on a control signal. This will ensure that only one module is driving the signal at a time, avoiding the multi-source error. Alternatively, you can also use a tri-state buffer controlled by the same control signal to achieve the same result. It is important to make sure that the control signal is synchronized with the clock to avoid any glitches or timing issues.
 

Related to [VHDL] Xilinx Multi-source error

1. What is a multi-source error in VHDL?

A multi-source error in VHDL occurs when there are conflicting signal assignments to the same signal in a design. This can happen when two or more processes or entities try to assign a value to the same signal at the same time.

2. How can I identify a multi-source error in VHDL?

A multi-source error can be identified by analyzing the error messages generated by the VHDL compiler. The error message will usually mention a "multi-source" or "multiple drivers" error and specify the signal that is causing the issue.

3. What can cause a multi-source error in VHDL?

A multi-source error can be caused by a variety of reasons, such as multiple processes or entities trying to assign a value to the same signal, incorrect use of shared variables, or missing or incorrect sensitivity lists in processes.

4. How can I fix a multi-source error in VHDL?

The first step to fixing a multi-source error is identifying the source of the conflict. This can be done by carefully analyzing the code and the error messages. Once the source is identified, the next step is to resolve the conflict by either removing one of the conflicting assignments, using shared variables instead of signals, or adding appropriate synchronization to ensure only one process or entity is assigning a value to the signal at a time.

5. Are there any tools or techniques to avoid multi-source errors in VHDL?

Yes, there are several techniques that can help avoid multi-source errors in VHDL, such as using shared variables instead of signals, carefully designing the architecture and processes to avoid conflicts, and using synchronization techniques such as semaphores or mutexes. Additionally, regular code reviews and thorough testing can also help catch and prevent multi-source errors in VHDL.

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