Altera ALTDLL - Manual (Page 5)

© February 2012 Altera Corporation ALTDLL and ALTDQ_DQS Megafunctions User Guide
1. About these Megafunctions
The ALTDLL and ALTDQ_DQS megafunctions provide a custom external memory
interface solution to access an FPGA's architecture and allow you to build your own
custom external memory interface physical layer (PHY) blocks.
Altera ® recommends that you use the ALTDLL and ALTDQ_DQS megafunctions
when implementing a specialized or customized intellectual property (IP) for an
Altera-supported external memory interface that is not supported in Altera's IP or a
proprietary interface that is not supported by Altera.
The ALTDLL and ALTDQ_DQS custom external memory interface solution offers
more efficient logic synthesis and device implementation, and saves valuable design
time if you choose to code your own logic. The ALTDLL megafunction configures the
dedicated DQS phase-shift circuitry, and the ALTDQ_DQS megafunction implements
the read and write PHY required for the interface.
While the ALTDLL and ALTDQ_DQS custom external memory interface solution is
primarily for building custom memory interface PHY blocks, you can also use this
solution to interface with any external device, such as ASIC, ASSP or another FPGA,
through the double data rate (DDR) interface.
1
The ALTDLL and ALTDQ_DQS megafunctions are specifically for memory interfaces
that support memory burst lengths of two. For common memory interfaces that
support memory burst lengths of four, Altera recommends that you use the
ALTMEMPHY- or UniPHY-based memory controllers to take advantage of the
benefits of Altera's IP and timing closure methodologies.
f For more information about the ALTMEMPHY- or UniPHY-based memory controllers
that Altera offers, refer to the
volume 3 of the External Memory Interface Handbook.
Device Support
The ALTDLL and ALTDQ_DQS megafunctions support the following Altera device
families:
■ Arria ® II GX
■ HardCopy ® III
■ HardCopy IV
■ Stratix ® III
■ Stratix IV