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W9725G6KB25A Datasheet(HTML) 29 Page - Winbond

Part No. W9725G6KB25A
Description  DLL aligns DQ and DQS transitions with clock, Data masks (DM) for write data, Write Data Mask
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Maker  WINBOND [Winbond]
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W9725G6KB25A Datasheet(HTML) 29 Page - Winbond

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W9725G6KB
Publication Release Date: Sep. 03, 2012
- 29 -
Revision A03
Table 5
– Precharge & Auto-precharge clarifications
From
Command
To Command
Minimum Delay between “From
Command” to “To Command”
Unit
Notes
Read
Precharge (to same Bank as Read)
AL + BL/2 + max(RTP, 2) - 2
clks
1, 2
Precharge All
AL + BL/2 + max(RTP, 2) - 2
clks
1, 2
Read w/AP
Precharge (to same Bank as Read w/AP)
AL + BL/2 + max(RTP, 2) - 2
clks
1, 2
Precharge All
AL + BL/2 + max(RTP, 2) - 2
clks
1, 2
Write
Precharge (to same Bank as Write)
WL + BL/2 + tWR
clks
2
Precharge All
WL + BL/2 + tWR
clks
2
Write w/AP
Precharge (to same Bank as Write w/AP)
WL + BL/2 + WR
clks
2
Precharge All
WL + BL/2 + WR
clks
2
Precharge
Precharge (to same Bank as Precharge)
1
clks
2
Precharge All
1
clks
2
Precharge
All
Precharge
1
clks
2
Precharge All
1
clks
2
Notes:
1. RTP[cycles] = RU{ tRTP[nS] / tCK(avg)[nS] }, where RU stands for round up.
2. For a given bank, the precharge period should be counted from the latest precharge command, either one bank precharge or
precharge all, issued to that bank. The precharge period is satisfied after tRP depending on the latest precharge command
issued to that bank.
8.8
Refresh Operation
DDR2 SDRAM requires a refresh of all rows in any rolling 64 mS interval. The necessary refresh can
be generated in one of two ways: by explicit Auto Refresh commands or by an internally timed Self
Refresh mode. Dividing the number of device rows into the rolling 64 mS interval defines the average
refresh interval, tREFI, which is a guideline to controllers for distributed refresh timing.
When CS , RAS and CAS are held LOW and WE HIGH at the rising edge of the clock, the chip
enters the Refresh mode (REF). All banks of the DDR2 SDRAM must be precharged and idle for a
minimum of the Precharge time (tRP) before the Refresh command (REF) can be applied. An address
counter, internal to the device, supplies the bank address during the refresh cycle. No control of the
external address bus is required once this cycle has started. (Example timing waveform refer to 11.28
Self Refresh diagram in Chapter 11)
8.9
Power Down Mode
Power-down is synchronously entered when CKE is registered LOW, along with NOP or Deselect
command. CKE is not allowed to go LOW while mode register or extended mode register command
time, or read or write operation is in progress. CKE is allowed to go LOW while any other operation
such as row activation, Precharge or Auto-precharge or Auto Refresh is in progress, but power down
IDD specification will not be applied until finishing those operations.
The DLL should be in a locked state when power-down is entered. Otherwise DLL should be reset
after exiting power-down mode for proper read operation.


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