w9425g8dh Winbond Electronics Corp America, w9425g8dh Datasheet - Page 10

• Manufacturer Part Number: w9425g8dh
• Description: 8m ? 4 Banks ? 8 Bits Ddr Sdram
• Manufacturer: Winbond Electronics Corp America

7.2.5
7.2.6
7.2.7
7.2.8
7.2.9
7.2.10 No-Operation Command
1) READA ≥ t
2) t
( RAS = "H", CAS = "L", WE = "L", BS0, BS1 = Bank, A10 = "H", A0 to A9 = Column Address)
The Write with Auto-precharge command performs the Precharge operation automatically after the
Write operation. This command must not be interrupted by any other commands.
( RAS = "H", CAS = "L", WE = "H", BS0, BS1 = Bank, A10 = "L", A0 to A9 = Column Address)
The Read command performs a Read operation to the bank designated by BS. The read data are
synchronized with both edges of DQS. The length of read data (Burst Length), Addressing Mode
and CAS Latency (access time from CAS command in a clock cycle) must be programmed in the
Mode Register at power-up prior to the Read operation.
( RAS = "H", CAS = ”L”, WE = ”H”, BS0, BS1 = Bank, A10 = ”H”, A0 to A9 = Column Address)
The Read with Auto-precharge command automatically performs the Precharge operation after the
Read operation.
( RAS = "L", CAS = "L", WE = "L", BS0 = "L", BS1 = "L", A0 to A12 = Register Data)
The Mode Register Set command programs the values of CAS Latency, Addressing Mode, Burst
Length and DLL reset in the Mode Register. The default values in the Mode Register after power-
up are undefined, therefore this command must be issued during the power-up sequence. Also,
this command can be issued while all banks are in the idle state. Refer to the table for specific
codes.
( RAS = "L", CAS = "L", WE = "L", BS0 = "H", BS1 = "L", A0 to A12 = Register data)
The Extended Mode Register Set command can be implemented as needed for function
extensions to the standard (SDR-SDRAM). These additional functions include DLL enable/disable,
output drive strength selection. The default value of the extended mode register is not defined;
therefore this command must be issued during the power-up sequence for enabling DLL. Refer to
the table for specific codes.
( RAS = "H", CAS = "H", WE = "H")
The No-Operation command simply performs no operation (same command as Device Deselect).
Internal precharge operation begins after BL/2 cycle from Read with Auto-precharge command.
Data can be read with shortest latency, but the internal Precharge operation does not begin until
after t
This command must not be interrupted by any other command.
RCD(min)
Write with Auto-precharge Command
Read Command
Read with Auto-precharge Command
Mode Register Set Command
Extended Mode Register Set Command
RAS (min)
≤ READA < t
RAS (min)
has completed.
- (BL/2) x t
RAS(min)
CK
- (BL/2) x t
- 10 -
CK
Publication Release Date: Nov. 20
Revision A4
,
2007