W949D6DB Datasheet, PDF (37/60 Pages) Winbond – Standard Self Refresh Mode

W949D6DB / W949D2DB
8.6.3 Write Burst (min. and max. tDQSS)
During Write bursts, the first valid data-in element will be registered on the first rising edge of DQS
following the WRITE command, and the subsequent data elements will be registered on successive
edges of DQS. The Low state of DQS between the WRITE command and the first rising edge is called
the write preamble, and the Low state on DQS following the last data-in element is called the write
postamble.
The time between the WRITE command and the first corresponding rising edge of DQS (tDQSS) is
specified with a relatively wide range - from 75% to 125% of a clock cycle. Following figure shows the
two extremes of tDQSS for a burst of 4. Upon completion of a burst, assuming no other commands have
been initiated, the DQs will remain high-Z and any additional input data will be ignored.
CK
CK
Command
Address
DQS
WRITE
NOP
BA,Col b
t_DQSSmin
DQ
DI b
DM
DQS
t_DQSSmax
DQ
DI b
DM
NOP
NOP
NOP
NOP
1) DI b = Data In to column b.
2) 3 subsequent elements of Data In are applied in the programmed order following DI b.
3) A non-interrupted burst of 4 is shown.
4) A10 is LOW with the WRITE command (Auto Precharge is disabled)
= Don't Care
8.6.4 Write to Write
Data for any WRITE burst may be concatenated with or truncated with a subsequent WRITE command.
In either case, a continuous flow of input data, can be maintained. The new WRITE command can be
issued on any positive edge of the clock following the previous WRITE command.
The first data-in element from the new burst is applied after either the last element of a completed burst
or the last desired data element of a longer burst which is being truncated. The new WRITE command
should be issued X cycles after the first WRITE command, where X equals the number of desired data-
in element pairs.
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Publication Release Date: Oct. 08, 2014
Revision: A01-003