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Row/Column open/close in SDRAM?

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cafukarfoo

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Hi Sir/Madam,

Can anyone share with me the meaning of the Row/Column open/close in SDRAM?

Thanks.
 

1: According to my understanding, there is no row open/close, just has column open/close with SDRAM.
2: For column open/close: I understanding is: the SDRAM is so big that you must identify which block you want to do write/read access to improve timing. For example: if the SDRAM is 1Mx16B. Then need decode 20bit address, the delay is huge. If you do column open, you can decode 8bit or 10bit address in advance, the in each read/write access you just need decode 12/10 bit address.
Because you has open a column, when you want to do write/read access on other column, of cause you need close the opned column first then open other column.
 
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    ivlsi

    ivlsi

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Hi yx yang,

Here is another statement:

SDRAM operate in 2 modes:
1. keep the current column open
2. close the column after read/write command

For first mode,
ater initial active command, subsequent access to the same row do not have to go through activation cycle. The disadvantage is that a access to a different row must execute additional precharge cycle.

1. Does precharge mean close the column?
2. Does other row need to be close before a new colum can be read if the column is from different row?
 

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