7
- Design verification (E.R.C.)
Overview.
- The function “Electrical Rules Check”
performs an automatic check.
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It points out any errors in a sheet, such as unconnected pins,
unconnected hierarchical symbols, shorted outputs…
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Naturally, an automatic check is not infallible, and the software
that make it possible to detect all design errors was not written
yet.
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But, such a control is very useful, because it allows you to detect
many oversights and small errors.
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In fact all the detected errors must be checked and then corrected
before proceeding as normal.
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The quality of check is directly related to the care taken in
declaring electrical pin properties during library creation.
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ERC errors are reported as “errors”
or “warnings”.
7.1
- Use.
- The Control of E.R.C. is launched by the icon
. -
Markers are placed on the elements causing an ERC error (pins, or
labels).
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Click on the markers, to view the corresponding diagnosis.
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You can also delete error markers from this menu.
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Example of ERC :

- One can see 4 errors :
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- Two outputs connected together.
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- Two inputs left unconnected.
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- An error on an invisible power port (power flag is
missing).
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Remark 1:
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Click on a marker, the diagnosis will be displayed.
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Remark 2:
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It is common to have an error (warning) on power pins, whereas all
seems normal (see example above).
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This is because, in most designs, the power is provided by
connectors, that aren't power sources (like regulator
output, which is declared as Power out).
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The ERC thus won't detect any Power out
pin to control this wire and will declare them not connected.
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You have to place a “PWR_FLAG” on such a power
port (which symbolizes in fact power output).

- The error marker then disappears.
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7.2
- Configuration
- The Options panel allows you to configure
connectivity rules to define electrical conditions for errors and
warnings :
-

- Rules can be changed
by clicking on the desired square of the matrix, causing it to cycle
through the choices : normal, warning, error.
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7.3
- ERC report file.
- An ERC report file can be saved by checking the option Write
ERC report.
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The file extension for
ERC report files is .erc.
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Here is an example:
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ERC control
(4/1/1997-14:16:4)
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***** Sheet 1 (INTERFACE
UNIVERSAL)
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ERC: Warning Pin input
Unconnected @ 8.450, 2.350
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ERC: Warning passive Pin
Unconnected @ 8.450, 1.950
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ERC: Warning: BiDir Pin
connected to power Pin (Net 6) @ 10.100, 3.300
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ERC: Warning: Power Pin
connected to BiDir Pin (Net 6) @ 4.950, 1.400
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>> Errors ERC: 4