concurrent auto precharge - memory controller

Hi all, I am designing a memory controller and I want to use concurrent auto precharge. I am using a micron SDR-SDRAM (

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). The datasheet doesnot specify how to activate a row in bank m when the current state is bank n. Is there a way I can specify the row that should be activated? and which row will be activated (figure 24 in pg:23) when current state of bank m is page active at T0 (same figure) ? Please tell me where I can learn more about this. Thanks for any help. Subhasri

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Subhasri krishnan
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Precharging means 'closing' a row so that a different row in that bank can be opened. The auto precharge example in Figure 24 assumes that the rows are already activated - remember, there can be several rows active at the same time as long as each row is in a different bank. In Figure

24, there is a row active in Bank n and a row active in Bank m. Figures 3 and 4 on page 12 show how to activate a row.
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Joe Samson
Pixel Velocity
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Joseph Samson

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Subhasri krishnan

When the datasheet talks about interrupting, they mean that a read or write burst is interrupted by another read or write cycle. Once the precharge happens, you have to wait Trp time before issuing another command.

From page 10: "The bank(s) will be available for a subsequent row access a specified time (tRP) after the PRECHARGE command is issued."

and

"Once a bank has been precharged, it is in the idle state and must be activated prior to any READ or WRITE commands being issued to that bank."

Yes, you have to issue an active command after a bank has been precharged, but each bank can have a row open simultaneously - you don't have to precharge Bank n in order to activate a row in Bank m.

--
Joe Samson
Pixel Velocity
Reply to
Joseph Samson

Reply to
Subhasri krishnan

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