158
T
Rp
ø
T
Rr
UCAS
,
LCAS
Software
standby
T
Rc3
HWR
(
WE
)
CSn
(
RASn
)
Note: n = 2 to 5
High
Figure 4.38 Self-Refresh Timing
In some DRAMs provided with a self-refresh mode, the
RAS
signal precharge time after self-
refreshing is longer than the normal precharge time. A setting can be made in bits TPCS2 to
TPCS0 in the REFCR register to make the precharge time after self-refreshing from 1 to 7 states
longer than the normal precharge time. In this case, too, normal precharging is performed
according to the setting of bits TPC1 and TPC0 in the DRACCR register, and therefore a setting
should be made to give the optimum post-self-refresh precharge time, including this time. Figure
4.39 shows an example of the timing when the precharge time after self-refreshing is extended by
2 states.
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