TMS570LC4357: EMIF SDRAM controller operation details

Part Number: TMS570LC4357

Hello,

I am looking for more details on the exact behavior of the SDRAM controller of the EMIF. 

In particular, I would like to understand if really all read/write accesses start with an ACT command, or if the memory controller is first checking if the row/bank is already open and then proceeds to the read/write operation skipping the ACT. 

Also it's not clear to me when an open row is closed since auto precharge is not used. 

Any information will be appreciated. 

Mathieu

  • Hello Mathieu,

    I have posed this question to one of our EMIF experts for further clarification and details. They are currently out of the office, but I am hopeful they will be able to provide an answer to me tomorrow (Friday). My apologies for the delay.

    Thanks and Regards,

    Chuck Davenport


    If this response answers your question, please indicate it by verifying the suggested answer when provided.

  • Hello Mathieu,

    My apologies for the delayed response as I had to touch base with our design support personnel to get a definitive answer on the internal workings of the EMIF.

    The EMIF does not always issue an ACT command before a read/write. The EMIF maintains a list of open row/banks. If the row/bank for a read/write command is open, the EMIF executes read/write without issuing an ACT command. If a row other than that required by the read/write is open, the EMIF will issue a PRECHARGE command to close the open row in that bank followed by an ACT command to open the required row, followed by the read/write.

    The EMIF does not implement auto-precharge. The EMIF will close row in a bank only when a different row in the same bank is required by a command. It also closes all row/banks before issuing refreshes, before low-power mode entry such as self-refresh, or if tRAS_max timer expires.

    Thanks and Regards,

    Chuck Davenport


    If this response answers your question, please indicate it by verifying the suggested answer when provided.

  • In reply to Chuck Davenport:

    Makes sense.
    Many thanks for the detailed and complete answer.

    Mathieu