
4/29/2020
Loongson 3A3000 / 3B3000 Processor User Manual
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Memory command merging and sorting improve overall bandwidth
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Configure register read and write ports, you can modify the basic parameters of the memory device
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Built-in dynamic delay compensation circuit (DCC) for reliable transmission and reception of data
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The ECC function can detect 1-bit and 2-bit errors on the data path, and can perform self-correction on 1-bit errors.
Error correction
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Support 133-667MHZ working frequency
9.2 DDR2 / 3 SDRAM read operation protocol
The protocol of DDR2 / 3 SDRAM read operation is shown in Figure 11-2. In the figure, the command (Command, referred to as CMD) is composed of RAS_n,
CAS_n and WE_n are composed of three signals. For read operations, RAS_n = 1, CAS_n = 0, and WE_n = 1.
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Godson 3A3000 / 3B3000 Processor User Manual • Volume 1
Figure 9- 1 DDR2 SDRAM read operation protocol
In the figure above, Cas Latency (CL) = 3, Read Latency (RL) = 3, and Burst Length = 8.
9.3 DDR2 / 3 SDRAM write operation protocol
The protocol of DDR2 / 3 SDRAM write operation is shown in Figure 11-3. The command CMD in the figure is composed of RAS_n, CAS_n and WE_n,
It consists of three signals. For write operations, RAS_n = 1, CAS_n = 0, and WE_n = 0. In addition, unlike read operations, write
The operation requires DQM to identify the mask of the write operation, that is, the number of bytes to be written. DQM is synchronized with the DQs signal in the figure.
Figure 9- 2 DDR2 SDRAM write operation protocol
In the above picture, Cas Latency (CL) = 3, Write Latency (WL) = Read Latency (RL) – 1 = 2,
Burst Length = 4.