DDR (Double Data Rate) SDRAM was introduced as a replacement for SDRAM memory running at bus speeds over 75MHz. DDR SDRAM is similar in function to the regular SDRAM but doubles the bandwidth of the memory by transferring data twice per cycle on both edges of the clock signal, implementing burst mode data transfer.
The DDR SDRAM Controller is a parameterized core giving user the flexibility for modifying the data widths, burst transfer rates, and CAS latency settings of the design. In addition, the DDR core supports intelligent bank management, which is done by maintaining a database of "all banks activated" and the "rows activated" in each bank. With this information, the DDR SDRAM Controller decides if an active or pre-charge command is needed. This effectively reduces the latency of read/write commands issued to the DDR SDRAM.