Why is the Maximum Fan-Out assignment ignored?

Description

Due to a problem in the Quartus® II software version 13.0 SP1 and earlier, you may see this warning if the Maximum Fan-Out assignment is applied to a register that drives an input of block RAM and the maximum block depth has been set.

Resolution

To work around this issue, perform one of the following options:

• Manually split the RAM into smaller blocks and duplicate the registers feeding the RAM inputs
• Do not set the maximum block depth

This problem is scheduled to be fixed in a future release of the Quartus II software.