title: Xilinx ISE: Should I be concerned about warning Xst:653?
body: <p>I never mention anything related to <code>GND_3_o</code> or <code>PWR_3_o</code> in my code. What are these signals, should I be concerned about these warnings related to them, and if so, how can I fix them?</p>
  
  <pre><code>WARNING:Xst:653 - Signal &lt;GND_3_o&gt; is used but never assigned. This sourceless signal will be automatically connected to value GND.
  WARNING:Xst:653 - Signal &lt;PWR_3_o&gt; is used but never assigned. This sourceless signal will be automatically connected to value GND.
  </code></pre>