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| HYB18L256169BF Datasheet, PDF (31/48 Pages) Qimonda AG – 256-Mbit Mobile-RAM | |||
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HY[B/E]18L256169BF-7.5
256-Mbit Mobile-RAM
Functional Description
2.4.8 PRECHARGE
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The PRECHARGE command is used to deactivate
(close) the open row in a particular bank or the open
row in all banks. The bank(s) will be available for a
subsequent row access a specified time (tRP) after the
PRECHARGE command is issued. Input A10
determines whether one or all banks are to be
precharged, and in the case where only one bank is to
be precharged, inputs BA0, BA1 select the bank.
Otherwise BA0, BA1 are treated as âDonât Careâ.
Once a bank has been precharged, it is in the idle state
and must be activated prior to any READ or WRITE
commands being issued to that bank. A PRECHARGE
command will be treated as a NOP if there is no open
row in that bank, or if the previously open row is already
in the process of precharging.
Figure 36 PRECHARGE Command
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.
Table 12 Timing Parameters for PRECHARGE
Parameter
Symbol
- 7.5
Units
min.
max.
ACTIVE to PRECHARGE command period
tRAS
45
100k
ns
WRITE recovery time
tWR
14
â
ns
PRECHARGE command period
tRP
19
â
ns
1) These parameters account for the number of clock cycles and depend on the operating frequency as follows:
no. of clock cycles = specified delay / clock period; round up to next integer.
Notes
1)
1)
1)
Data Sheet
31
Rev. 1.02, 2006-12
02032006-MP0M-7FQG
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