External Memory Interface Handbook Volume 3: Reference Material

ID 683841
Date 7/24/2019
Public
Document Table of Contents

6.6.4.2. Bank Policy

The bank policy of the SDRAM controller allows users to request that a transaction's bank remain open after an operation has finished so that future accesses do not delay in activating the same bank and row combination. The controller supports only eight simultaneously-opened banks, so an open bank might get closed if the bank resource is needed for other operations.

Open bank resources are allocated dynamically as SDRAM burst transactions are scheduled. Bank allocation is requested automatically by the controller when an incoming transaction spans multiple SDRAM bursts or by the extended command interface. When a bank must be reallocated, the least‑recently‑used open bank is used as the replacement.

If the controller determines that the next pending command will cause the bank request to not be honored, the bank might be held open or closed depending on the pending operation. A request to close a bank with a pending operation in the timer bank pool to the same row address causes the bank to remain open. A request to leave a bank open with a pending command to the same bank but a different row address causes a precharge operation to occur.

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