W942508CH Datasheet, PDF (22/47 Pages) Winbond – 8M x 4 BANKS x 8 BIT DDR SDRAM

W942508CH
The write command performs a Write operation to the bank designated by BS. The write data
are latched at both edges of DQS. The length of the write data (Burst Length) and column
access sequence (Addressing Mode) must be in the Mode Register at power-up prior to the
Write operation.
5. Write with Auto Precharge Command
( RAS ="H", CAS = "L", WE = "L", BS0, BS1 = Bank, A10= "H", A0 to A9, A11 = 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.
6. Read Command
( RAS ="H", CAS = "L", WE = "H", BS0, BS1 = Bank, A10 = "L", A0 to A9, A11 = 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.
7. Read with Auto Precharge Command
( RAS = "H", CAS = "L", WE = "H", BS0, BS1 = Bank, A10 = "H", A0 to A9, A11 = Column
Address)
The Read with Auto precharge command automatically performs the Precharge operation after
the Read operation.
1) READA ≥ tRAS (min) - (BL/2) x tCK
Internal precharge operation begins after BL/2 cycle from Read with Auto Precharge
command.
2) tRCD(min) ≤ READA < tRAS(min) - (BL/2) x tCK
Data can be read with shortest latency, but the internal Precharge operation does not begin
until after tRAS (min) has completed.
This command must not be interrupted by any other command.
8. Mode Register Set Command
( 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.
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