Implementing Double Data Rate

Implementing Double Data Rate I/O Signaling in Cyclone Devices

Double data rate (DDR) transmission is used in many applications where

fast data transmission is needed, such as memory access and first-in

first-out (FIFO) memory structures. DDR uses both edges of a clock to

transmit data, which facilitates data transmission at twice the rate of a

single data rate (SDR) architecture using the same clock speed. This

method also reduces the number of I/O pins required to transmit data.

This chapter shows implementations of a double data rate I/O interface

using Cyclone® devices. Cyclone devices support DDR input, DDR

output, and bidirectional DDR signaling.

f For more information on using Cyclone devices in applications with

DDR SDRAM and FCRAM memory devices, see “DDR Memory

Support” on page 10–4.