This version of the Lattice DDR SDRAM Controller does not have pipelining, and is significantly smaller than the pipelined version. 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 users the flexibility for modifying data widths, burst transfer rates and CAS latency settings in a 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.
DDR SDRAM Controller - Non-Pipelined
Overview
Key Features
- Performance of Greater than 133MHz (266 DDR)
- Interfaces to JEDEC Standard DDR SDRAMs
- Supports DDR SDRAM Data Widths of 16, 32 and 64 bits
- Supports up to 8 External Memory Banks
- Programmable Burst Lengths of 2, 4, or 8
- Programmable CAS Latency of 1.5, 2.0, 2.5 or 3.0
- Byte-level Writing Supported
- Supports Power-down and Self Refresh Modes
- Automatic Initialization
- Automatic Refresh During Normal and Power-down Modes
- Timing and Settings Parameters Implemented as Programmable Registers
- Complete Synchronous Implementation
Block Diagram
