【应用笔记】Cyclone器件和DDR SDRAM的接口(Interfacing DDR SDRAM with Cyclone Devices)
许多应用使用单数据速率(single data rate,SDR))存储器。然而，正如这些应用变得更加苛求，设计者需要找出提升新性能而不增加成本的方法。
Many applications use single data rate (SDR) memory. However, as these
applications become more demanding, designers need to find ways to
improve performance without increasing cost. Over the years, DRAM
companies introduced memory types with improved architecture such as
fast page mode (FPM), extended data out (EDO), and SDRAM to address
this issue. Double data rate (DDR) memory is the most popular memory
interface among these memory architectures because of its ability to
increase data bandwidth without increasing system complexity and cost.
DDR memory uses both edges of a clock to transmit data, which allows
data transmission at twice the rate of a SDR memory device at the same
clock speed and with the same number of I/O pins required to transmit
data. DDR memory is used in many applications where fast data
transmission is needed, such as memory access and first-in first-out
(FIFO) memory structures. Table 1 shows the Cyclone device support for
DDR SDRAM.an348.pdf