W9425G6DH データシートの表示（PDF） - Winbond

部品番号

コンポーネント説明

メーカー

W9425G6DH

4M × 4 BANKS × 16 BITS DDR SDRAM

Winbond 

W9425G6DH

7.5 Precharge

There are two Commands, which perform the precharge operation (Bank Precharge and Precharge

All). When the Bank Precharge command is issued to the active bank, the bank is precharged and

then switched to the idle state. The Bank Precharge command can precharge one bank independently

of the other bank and hold the unprecharged bank in the active state. The maximum time each bank

can be held in the active state is specified as tRAS (max). Therefore, each bank must be precharged

within tRAS(max) from the bank activate command.

The Precharge All command can be used to precharge all banks simultaneously. Even if banks are

not in the active state, the Precharge All command can still be issued. In this case, the Precharge

operation is performed only for the active bank and the precharge bank is then switched to the idle

state.

7.6 Burst Termination

When the Precharge command is used for a bank in a Burst cycle, the Burst operation is terminated.

When Burst Read cycle is interrupted by the Precharge command, read operation is disabled after

clock cycle of (CAS Latency) from the Precharge command. When the Burst Write cycle is interrupted

by the Precharge command, the input circuit is reset at the same clock cycle at which the precharge

command is issued. In this case, the DM signal must be asserted "high" during tWR to prevent writing

the invalided data to the cell array.

When the Burst Read Stop command is issued for the bank in a Burst Read cycle, the Burst Read

operation is terminated. The Burst read Stop command is not supported during a write burst operation.

Refer to the diagrams for Burst termination.

7.7 Refresh Operation

Two types of Refresh operation can be performed on the device: Auto Refresh and Self Refresh. By

repeating the Auto Refresh cycle, each bank in turn refreshed automatically. The Refresh operation

must be performed 8192 times (rows) within 64mS. The period between the Auto Refresh command

and the next command is specified by tRFC.

Self Refresh mode enters issuing the Self Refresh command (CKE asserted "low") while all banks are

in the idle state. The device is in Self Refresh mode for as long as CKE held "low". In the case of

distributed Auto Refresh commands, distributed auto refresh commands must be issued every 7.8 µS

and the last distributed Auto Refresh commands must be performed within 7.8 µS before entering the

self refresh mode. After exiting from the Self Refresh mode, the refresh operation must be performed

within 7.8 µS. In Self Refresh mode, all input/output buffers are disabled, resulting in lower power

dissipation (except CKE buffer). Refer to the diagrams for Refresh operation.

7.8 Power Down Mode

Two types of Power Down Mode can be performed on the device: Active Standby Power Down Mode

and Precharge Standby Power Down Mode.

When the device enters the Power Down Mode, all input/output buffers and DLL are disabled resulting

in low power dissipation (except CKE buffer).

Power Down Mode enter asserting CKE "low" while the device is not running a burst cycle. Taking

CKE "high" can exit this mode. When CKE goes high, a No operation command must be input at next

CLK rising edge. Refer to the diagrams for Power Down Mode.

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Publication Release Date:Nov. 20, 2007

Revision A7

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