Section 13 Bus State Controller (BSC)
SH7751 Group, SH7751R Group
Page 424 of 1128
R01UH0457EJ0301 Rev. 3.01
Sep 24, 2013
Refresh:
The bus state controller includes a function for controlling DRAM refreshing.
Distributed refreshing using a CAS-before-RAS cycle can be performed for DRAM by clearing
the RMODE bit to 0 and setting the RFSH bit to 1 in MCR. Self-refresh mode is also supported.
•
CAS-before-RAS Refresh
When CAS-before-RAS refresh cycles are executed, refreshing is performed at intervals
determined by the input clock selected by bits CKS2–CKS0 in RTCSR, and the value set in
RTCOR. The value of bits CKS2–CKS0 in RTCOR should be set so as to satisfy the
specification for the DRAM refresh interval. First make the settings for RTCOR, RTCNT, and
the RMODE and RFSH bits in MCR, then make the CKS2–CKS0 setting. When the clock is
selected by CKS2–CKS0, RTCNT starts counting up from the value at that time. The RTCNT
value is constantly compared with the RTCOR value, and if the two values are the same, a
refresh request is generated and the
BACK
pin goes high. If this LSI external bus can be used,
CAS-before-RAS refreshing is performed. At the same time, RTCNT is cleared to zero and the
count-up is restarted. Figure 13.20 shows the operation of CAS-before-RAS refreshing.
RTCNT value
RTCOR-1
H'00000000
RTCSR.CKS2–0
External bus
Refresh request cleared
by start of refresh cycle
= 000
≠
000
RTCNT cleared to 0 when
RTCNT = RTCOR
CAS-before-RAS refresh cycle
Time
Refresh
request
Figure 13.20 CAS-Before-RAS Refresh Operation
Figure 13.21 shows the timing of the CAS-before-RAS refresh cycle.
The number of RAS assert cycles in the refresh cycle is specified by bits TRAS2–TRAS0 in
MCR. The specification of the RAS precharge time in the refresh cycle is determined by the
setting of bits TRC2–TRC0 in MCR.
Содержание SH7751 Group
Страница 2: ...Page ii of liv R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 30: ...Page xxx of liv R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 46: ...Page xlvi of liv R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 54: ...Page liv of liv R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 190: ...Section 4 Caches SH7751 Group SH7751R Group Page 136 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 226: ...Section 5 Exceptions SH7751 Group SH7751R Group Page 172 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 264: ...Section 7 Instruction Set SH7751 Group SH7751R Group Page 210 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 320: ...Section 9 Power Down Modes SH7751 Group SH7751R Group Page 266 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 344: ...Section 10 Clock Oscillation Circuits SH7751 Group SH7751R Group Page 290 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 388: ...Section 12 Timer Unit TMU SH7751 Group SH7751R Group Page 334 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
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 ...
Страница 1185: ......
Страница 1186: ... SH7751 Group SH7751R Group User s Manual Hardware R01UH0457EJ0301 Previous Number REJ09B0370 0400 ...