Doubt on DDR SDRAM read/write operation sequence.

Hi all, I activate row R1 and Bank B1.After time Trcd read from Bank B1 and Column C1.Suppose next I want to read from the same row R1 but different Bank B2 should I precharge the row then issue a new Active command or issue a read command with Bank B2 or should I issue new Active command with Row R1 and bank B2 then issue read command.

Please throw light on it.

Thanks in advance...


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The way to think about it is that each bank is a separate DRAM chip which can be closed (precharged) or open on a particular row. So, the fact that you switch to the same row in a different bank is completely irrelevant. What matters is the state of that bank.

Now what probably could have confused you is that a lot of simple SDRAM controllers (such as previous version from XESS) only track the currently active bank, but AFAIR the lastest actually track each bank and can avoid reopening the row when not strictly needed. One of the nice benefits of this is fast access for multiple memory streams (sequential memory accesses) as long as they hit in different banks.

Hope that helped, Tommy

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Tommy Thorn

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