W949D6DB Datasheet, PDF (42/60 Pages) Winbond – Standard Self Refresh Mode

W949D6DB / W949D2DB
8.7.1 Precharge Command
CK
CK
CKE
CS
(High)
RAS
CAS
WE
Address
A10
BA0,BA1
All Banks
One Bank
BA
= Don't Care
BA = Bank Address
(if A10 = L, otherwise Don't Care)
8.8 Auto Precharge
Auto Precharge is a feature which performs the same individual bank precharge function as described
above, but without requiring an explicit command. This is accomplished by using A10 (A10 = High), 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. Auto Precharge is non persistent in that it is either enabled or
disabled for each individual READ or WRITE command.
Auto Precharge ensures that a precharge is initiated at the earliest valid stage within a burst. The user
must not issue another command to the same bank until the precharing time (tRP) is completed. This is
determined as if an explicit PRECHARGE command was issued at the earliest possible time, as
described for each burst type in the Operation section of this specification.
8.9 Refresh Requirements
LPDDR SDRAM devices require a refresh of all rows in any rolling 64mS interval. Each refresh is
generated in one of two ways: by an explicit AUTO REFRESH command, or by an internally timed event
in SELF REFRESH mode. Dividing the number of device rows into the rolling 64mS interval defines the
average refresh interval (tREFI), which is a guideline to controllers for distributed refresh timing.
- 42 -
Publication Release Date: Oct. 08, 2014
Revision: A01-003