W949D6DB Datasheet, PDF (16/60 Pages) Winbond – Standard Self Refresh Mode

W949D6DB / W949D2DB
7.3.3 Burst Type
Accesses within a given burst may be programmed to be either sequential or interleaved; this is referred
to as the burst type and is selected via bit A3. The ordering of accesses within a burst is determined by
the burst length, the burst type and the starting column address, as shown in the previous table.
7.3.4 Read Latency
The CAS latency is the delay between the registration of a READ command and the availability of the
first piece of output data. The latency should be set to 2 or 3 clocks, as shown in section 7.3 Mode
Register Definition figure.
If a READ command is registered at a clock edge n and the latency is 3 clocks, the first data element
will be valid at n + 2 tCK + tAC. If a READ command is registered at a clock edge n and the latency is 2
clocks, the first data element will be valid at n + tCK + tAC.
7.4 Extended Mode Register Description
The Extended Mode Register controls functions beyond those controlled by the Mode Register; these
additional functions include output drive strength selection and Partial Array Self Refresh (PASR). PASR
is effective in Self Refresh mode only.
The Extended Mode Register is programmed via the MODE REGISTER SET command (with BA1=1
and BA0=0) and will retain the stored information until it is reprogrammed, the device is put in Deep
Power Down mode, or the device loses power.
The Extended Mode Register must be loaded when all banks are idle and no bursts are in progress,
and the controller must wait the specified time tMRD before initiating any subsequent operation.
Violating either of these requirements will result in unspecified operation.
Address bits A0-A2 specify PASR, A5-A7 the Driver Strength. A logic 0 should be programmed to all
the undefined addresses bits to ensure future compatibility.
Reserved states should not be used, as unknown operation or incompatibility with future versions may
result.
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Publication Release Date: Oct. 08, 2014
Revision: A01-003