AR# 16224


8.1is3 IBISWriter - Warning message: "No model is available for IOB <pin_name> for configuration value: DIRECTION:BIDIR"


Keywords: IBIS, model, input, output, DCI, bi-directional, bidirectional, SSTL, HSTL, warning

IBISWriter is unable to generate models for bidirectional DCI I/Os. The following message is seen when IBISWriter is run:

"No model is available for IOB <pin_name> for configuration value: DIRECTION:BIDIR - Input and/or Output Models may be available."


Distinct input and output IBIS models are required for DCI I/Os, because of the way these models are generated. Since IBISWriter does not find a single model that matches the bidirectional DCI configuration, it gets confused and does not generate any model at all.

To work around this issue:
1 - In your UCF, locate any IOSTANDARD settings that represent I/Os that are both DCI and bidirectional.
2 - Change these IOSTANDARD settings to a different standard, preferably one that is not used elsewhere in the design.
3 - Make a copy of your original design and implement through the Map step. PAR is not necessary.
4 - Run IBISWriter from the command line, using your <my_design>_map.ncd file as the input.
5 - Download the latest version of your target device family's IBIS file from the web:
6 - In the IBIS file you just downloaded, locate the input and output models for your bidirectional DCI I/Os of interest. For example, "SSTL2_II_DCI_I" and "SSTL2_II_DCI_O."
7 - Copy these models into the IBIS file you generated in step (4), replacing the models that were generated for the IOSTANDARD changes you made in step (2).
8 - Modify model names in the IBIS file's [Pin] list to account for the changes in step (7).

A fix to IBISWriter is pending. For more information, please contact Xilinx Technical Support.
AR# 16224
Date 12/06/2009
Status Archive
Type General Article
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