Why does the rx_byteorderalignstatus output port not get asserted on the first occurrence of the byte ordering pattern in Basic double-width configuration in Stratix IV GX device?

Solution

For Stratix® IV GX devices, the ALTGX MegaWizard® Plug-in Manager provides an option to select rx_syncstatus output signal based byte ordering. This option is available in the Rate Matcher/Byte Order screen. If this option is selected, the byte ordering block is triggered when rx_syncstatus gets asserted.

Altera has identified that during functional simulation in Quartus® II software version 8.0,  the  rx_byteorderalignstatus port does not get asserted on the first occurrence of the byte ordering pattern for the following basic double width mode configuration.

• FPGA Fabric-Transceiver interface width: 32-bits
• 8b10b encoder/decoder disabled
• Word aligner pattern width: 32-bits (ex: 1A2B3C4D)
• Byte ordering pattern width: 16-bits
• Byte ordering pattern: 2 LSBytes of the word aligner pattern (ex: 3C4D)

For the above configuration, the byte ordering block receives rx_syncstatus one clock cycle after receiving the word aligned data that contains the byte ordering pattern. Therefore the rx_byteorderalignstatus port does not get asserted on the first occurrence of the byte ordering pattern.

Workaround : This issue will be fixed in Quartus® II software version 8.1