xapp134 verilog代碼

The SDRAM controller is designed for the Virtex V300bg432-6. It's simulated with Micron SDRAM models.? The design is verified with backannotated simulation at 125MHz
1. Is RAS to CAS delay programmable?
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? . No, the data registers has a fixed number of pipeline stages.? This reference design supports RAS-to-CAS delay of 2 clock cycles.? If you need to adjust to a different RAS-to-CAS delay, change the SRL16 Address values in sys_int.v.? The address value should be (Trcd/Tck) +1
? . Note, you still need to write the RAS-to-CAS value to the Controller's Mode Reg during PRECHARGE command.? The value should be (Trcd/Tck) -2

2. How do I modify the design to support 128Mb/256Mb SDRAM parts with a 64-bit data bus?
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? . You'll need to add more IO buffers for the extra data and address signals (in sdrm.v)
? . You'll need to change ADDR_MSB and DATA_MSB (in define.v)
? . In the current design, instead of 1 tristate signal for the Data lines,
??? we duplicate it to 4 signals, each having 8 loads.?
??? This was done to reduce net delays on that tristate signal.?
??? You may need to add 4 more tristate lines if you're going to 64-bit.?
??? The tristate signal is sd_doe_n in sdrm.v