Article ID: 000077721 Content Type: Troubleshooting Last Reviewed: 09/02/2012

Why is CAS latency of 2 or 2.5 not supported for DDR SDRAM Altmemphy or DDR SDRAM High Performance Controller?

Environment

BUILT IN - ARTICLE INTRO SECOND COMPONENT
Description

The reason CAS latency of less than 3 are not supported for DDR SDRAM Altmemphy and DDR SDRAM High Performance Controller is due to the postamble logic path having a minimum enable latency from address output to dqs enable time. On Stratix® II, Stratix III, Stratix IV along with Arria® GX and Arria II GX devices this latency is too long and hence requires CAS latency of greater than 2 or 2.5 to work reliably. There is no fix/workaround to implement CAS latency of 2 or 2.5.

You will have to set CAS latency of 3 even for lower speeds.

Related Products

This article applies to 8 products

Arria® GX FPGA
Stratix® II GX FPGA
Stratix® II FPGAs
Stratix® IV GX FPGA
Stratix® III FPGAs
Arria® II GX FPGA
Stratix® IV GT FPGA
Stratix® IV E FPGA

Disclaimer

1

All postings and use of the content on this site are subject to Intel.com Terms of Use.