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Self-Refresh: When both the RMD and RFSH bits of the RTCSR are set to 1, the
CAS
signal and
RAS
signal are output and the DRAM enters self-refresh mode, as shown in figure 10.16. Do not
access DRAM during self-refreshes, in order to preserve DRAM data. When performing DRAM
accesses, first cancel the self-refresh, then access only after doing individual refreshes for all row
addresses within the time prescribed for the particular DRAM.
For external bus right requests during self-refreshes, to preserve DRAM data at the time of
releasing the bus rights, only
CASx
,
RAS
, and RDWR are output and the bus rights are released to
the external device with the self-refresh maintained. Consequently, do not perform DRAM
accesses from external devices at such a time.
CK
CASx
RAS
T
Rp
T
Rr1
T
Rr2
T
Rc
T
Rc
Figure 10.16 Self-Refresh Timing
Содержание SH7041 Series
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