RAS Precharge (tRP)

After data is gathered from the memory, a command called Precharge needs to be issued, closing the memory row that was being used and allowing a new row to be activated. RAS Precharge time (tRP) is the time taken between the Precharge command and the next Active command can be issue. As we learned from the previous page, the “active” command starts a read or write cycle.

click to enlarge
Figure 6: RAS Precharge (tRP).

On Figure 6 we are giving an example of a memory with tRP = 3.

As it happens with the other parameters, RAS Precharge works with the memory real clock (which is half the memory labeled clock), and the lower this parameter is, the faster the memory will be, as it will issue the “active” command earlier.

Adding everything we’ve seen, the time elapsed between issuing the Precharge command and actually getting the data will be tRP + tRCD + CL.

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