Data Sheet
HY[B/E]18M1G16[0/1]BF
1-Gbit DDR Mobile-RAM
2.4.8.1
AUTO PRECHARGE
Auto Precharge is a feature which performs the same individual-bank precharge functions described above, but 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. Auto Precharge is non persistent 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. The user must not issue another
command to the same bank until the precharge (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.
2.4.9
AUTO REFRESH and SELF REFRESH
The DDR Mobile-RAM requires a refresh of all rows in an 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
rows into the rolling 64ms interval defines the average refresh interval, tREFI, which is a guideline to controllers for distributed
refresh timing.
2.4.9.1
AUTO REFRESH
Auto Refresh is used during normal operation of the DDR
Mobile-RAM. The command is non persistent, so it must be
issued each time a refresh is required. A minimum time tRFC
is required between two AUTO REFRESH commands. The
same rule applies to any access command after the Auto
Refresh operation. All banks must be precharged prior to the
AUTO REFRESH command.The refresh addressing is
generated by the internal refresh controller. This makes the
address bits “Don’t Care” during an AUTO REFRESH
command. The DDR Mobile-RAM requires Auto Refresh
cycles at an average periodic interval of tREFI (max.).Partial
array mode has no influence on Auto Refresh mode.
FIGURE 33
AUTO REFRESH Command
CK
CK
CKE
(High)
CS
RAS
CAS
WE
To allow for improved efficiency in scheduling and switching
between tasks, some flexibility in the absolute refresh interval
is provided.
A maximum of eight AUTO REFRESH
commands can be posted to the DDR Mobile-RAM, and the
maximum absolute interval between any AUTO REFRESH
command and the next AUTO REFRESH command is 8 *
A0-A12
BA0,BA1
tREFI
.
= Don't Care
Rev.1.0, 2007-03
42
10242006-Y557-TZXW
QIMONDA [ QIMONDA AG ]
