Why does the busy port of the ALT2GXB_Reconfig megafunction get stuck at high during some reconfiguration operations?

The busy port of the ALT2GXB_reconfig megafunction gets stuck at a high logic value if you perform operations that are not supported by the dynamic reconfiguration controller. The behavior occurs during simulation and during device operation in silicon.

The following list provides some examples of unsupported operations:

• Enabling the Analog controls input ports but not the output ports in the megafunction, and then performing a read operation to read the analog control values (VOD, equalization, dcgain, and preemphasis). For example the busy port gets stuck at high, if you enable the tx_vodctrl port and not the tx_vodctrl_out port, and you attempt to read the analog control values during run-time.
• Issuing a read operation for any reconfiguration mode other than the Analog controls mode.
• Using an unsupported value on the reconfig_mode_sel port and performing a write operation.

The ALT2GXB_reconfig megafunction cannot recover if the busy signal gets into a stuck state. To avoid this problem, do not perform operations that are not supported by the dynamic reconfiguration controller.

For more information about operations supported by the dynamic reconfiguration controller, refer to the Dynamic Reconfiguration section in the Stratix II GX Transceiver Architecture Overview (PDF) chapter in volume 2 of the Stratix II GX Handbook.