【应用手册】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.
cyc_c51010(Replaces AN256) .pdf