Compilation of a design targeting Stratix IV GX devices that contains an ALTGX megafunction fails with the error Error: One or more transceiver atoms cannot be placed

Description

In the MegaWizard Plug-In Manager for Stratix IV GX ALTGX megafunctions, if you select XN in the Which subprotocol will you be using box and then select None in the same box, the MegaWizard Plug-In Manager generates incorrect parameters. During compilation, these incorrect parameters cause fitting to fail with errors similar to the following:

Error: One or more transceiver atoms cannot be placed

Resolution

Do not change the subprotocol setting from None to XN and then back to None.