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.