DDR3 参数详解

1. 时间参数：

CAS Latency
The CAS latency is the delay, in clock cycles, between sending a READ command and the moment the first pice of data is available on the outputs.
简称: CL. 是DDR的重要参数，用来表示发出读命令到管脚接收到数据之间的时间。

tWR - Write Recovery Time:
tWR is the number of clock cycles taken between writing data and issuing the precharge command. tWR is necessary to guarantee that all data in the write buffer can be safely written to the memory core.


tRAS - Row Active Time:
tRAS is the number of clock cycles taken between a bank active command and issuing the precharge command.


tRC - Row Cycle Time:
The minimum time interval between successive ACTIVE commands to the same bank is defined by tRC.
tRC = tRAS + tRP


tRCD - Row Address to Column Address Delay:
tRCD is the number of clock cycles taken between the issuing of the active command and the read/write command. In this time the internal row signal settles enough for the charge sensor to amplify it.
行选通周期。此参数表示发出行命令和bank命令到信号稳定后可以发送列命令和读/写命令之间的时间。

tRP - Row Precharge Time:
tRP is the number of clock cycles taken between the issuing of the precharge command and the active command. In this time the sense amps charge and the bank is activated.
DDR重要参数：表示行预充电时间。读取不同行（同一bank或不同bank）需要的转换时间。

tRRD - Row Active to Row Active Delay:
The minimum time interval between successive ACTIVE commands to the different banks is defined by tRRD.


tCCD - Column Address to Column Address Delay


tRD - Active to Read Delay ?:


tWTR - Internal Write to Read Command Delay:
tWTR is the delay that has to be inserted after sending the last data from a write operation to the memory and issuing a read command.


tRDA - Read Delay Adjust

tAC ： Access time from clock
表示命令被读取后经过S-AMP放大传输到I/O脚的时间。

Memory timings are given as: CAS-tRCD-tRP