W989D6DB Datasheet, PDF (18/64 Pages) Winbond – Standard Self Refresh Mode

W989D6DB / W989D2DB
8.2 Write Operation
Issuing the Write command after t_RCD from the Bank Activate command, the input data is latched sequentially,
synchronizing with the positive edges of CLK after the Write command (Burst Write operation). The burst length of
the Write data (Burst Length) and Addressing Mode must be set in the Mode Register at power-up.
When the Write with Auto Precharge command is issued, the Precharge operation is performed automatically
after the Write cycle, then the bank is switched to the idle state. This command cannot be interrupted by any other
command for the entire burst data duration. Also, when the Burst Length is 1 and tRCD (min), the timing from the
RAS command to the start of the Auto Precharge operation is shorter than tRAS (min). In this case, tRAS (min)
must be satisfied by extending tRCD.
When the Precharge operation is performed in a bank during a Burst Write operation, the Burst operation is
terminated.
When the Burst Length is full-page, the input data is repeatedly latched until the Burst Stop command or the
Precharge command is issued.
When the Burst Read and Single Write mode is selected, the write burst length is 1 regardless of the read burst
length.
8.3 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 precharged bank is then switched to the idle state.
8.3.1 Auto Precharge
Auto precharge is a feature that performs the same individual-bank PRECHARGE function described previously,
without requiring an explicit command. This is accomplished by using A10 to enable auto precharge in
conjunction with a specific READ or WRITE command. A precharge of the bank/row that is addressed with the
READ or WRITE command is automatically performed upon completion of the READ or WRITE burst, except in
the continuous page burst mode where auto precharge does not apply. In the specific case of write burst mode
set to single location access with burst length set to continuous, the burst length setting is the overriding setting
and auto precharge does not apply. Auto precharge is nonpersistent in that it is either enabled or disabled for
each individual READ or WRITE command.
Auto precharge ensures that the precharge is initiated at the earliest valid stage within a burst. Another command
cannot be issued to the same bank until the precharge time (tRP) is completed. This is determined as if an explicit
PRECHARGE command was issued at the earliest possible time.
Winbond SDRAM supports concurrent auto precharge; cases of concurrent auto precharge for READs and
WRITEs are defined below.
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Publication Release Date: Mar. 19, 2014
Revision: A01-001