Why does my simple dual-port memory not function correctly in RTL simulation?

Description

Due to a problem in the Quartus® II software version 11.1 and later, the altsyncram simulation model incorrectly delays the output data by one extra clock cycle when reading from a simple dual-port memory implemented using MLAB resources. This issue occurs when the read-during-write option is set to Old data.

Resolution

A patch is available to fix this problem in the Quartus II software version 11.1 SP2. Download and install patch 2.32 from the appropriate link below:

• Download the version 11.1 SP2 patch 2.32 for Windows (.exe)
• Download the version 11.1 SP2 patch 2.32 for Linux (.tar)
• Download the Readme for the Quartus II software version 11.1 SP2 patch 2.32 (.txt)

This problem is fixed beginning with the Quartus II software version 12.0 SP1.