Section 13 Bus State Controller (BSC)
SH7751 Group, SH7751R Group
Page 426 of 1128
R01UH0457EJ0301 Rev. 3.01
Sep 24, 2013
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Relationship between Refresh Requests and Bus Cycle Requests
If a refresh request is generated during execution of a bus cycle, execution of the refresh is
deferred until the bus cycle is completed. Refresh operations are deferred during multiple bus
cycles generated because the data bus width is smaller than the access size (for example, when
performing longword access to 8-bit bus width memory) and during a 32-byte transfer such as
a cache fill or write-back, and also between read and write cycles during execution of a TAS
instruction, and between read and write cycles when DMAC dual address transfer is executed.
If a refresh request occurs when the bus has been released by the bus arbiter, refresh execution
is deferred until the bus is acquired. If a match between RTCNT and RTCOR occurs while a
refresh is waiting to be executed, so that a new refresh request is generated, the previous
refresh request is eliminated. In order for refreshing to be performed normally, care must be
taken to ensure that no bus cycle or bus mastership occurs that is longer than the refresh
interval. When a refresh request is generated, the
BACK
pin is negated (driven high).
Therefore, normal refreshing can be performed by having the
BACK
pin monitored by a bus
master other than this LSI requesting the bus, or the bus arbiter, and returning the bus to this
LSI.
TRr2
TRr3
TRr4
TRr5
Trc
TRr1
Trc
Trc
CKIO
A25–A0
CSn
RD/
WR
RAS
CAS
D31–D0
BS
Figure 13.22 DRAM Self-Refresh Cycle Timing
Содержание SH7751 Group
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Страница 800: ...Section 17 Smart Card Interface SH7751 Group SH7751R Group Page 746 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 848: ...Section 19 Interrupt Controller INTC SH7751 Group SH7751R Group Page 794 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 876: ...Section 20 User Break Controller UBC SH7751 Group SH7751R Group Page 822 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 1036: ...Section 22 PCI Controller PCIC SH7751 Group SH7751R Group Page 982 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 1152: ...Appendix C Mode Pin Settings SH7751 Group SH7751R Group Page 1098 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
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