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Section 12 Bus State Controller (BSC)
Rev. 4.00 Sep. 14, 2005 Page 368 of 982
REJ09B0023-0400
Relationship between Refresh Requests and Bus Cycles: If a refresh request occurs during bus
cycle execution, the refresh cycle must wait for the bus cycle to be completed. If a refresh request
occurs while the bus is released by the bus arbitration function, the refresh will not be executed
until the bus mastership is acquired.
If a new refresh request occurs while waiting for the previous refresh request, the previous refresh
request is deleted. To refresh correctly, a bus cycle longer than the refresh interval or the bus
mastership occupation must be prevented from occurring. If a bus mastership is requested during
self-refresh, the bus will not be released until the refresh is completed.
Low-Frequency Mode: When the SLOW bit in SDCR is set to 1, output of commands, addresses,
and write data, and fetch of read data are performed at a timing suitable for operating SDRAM at a
low frequency.
Figure 12.31 shows the access timing in low-frequency mode. In this mode, commands, addresses,
and write data are output in synchronization with the falling edge of CKIO, which is half a cycle
delayed than the normal timing. Read data is fetched at the rising edge of CKIO, which is half a
cycle faster than the normal timing. This timing allows the hold time of commands, addresses,
write data, and read data to be extended.
If SDRAM is operated at a high frequency with the SLOW bit set to 1, the setup time of
commands, addresses, write data, and read data are not guaranteed. Take the operating frequency
and timing design into consideration when making the SLOW bit setting.
Содержание HD6417641
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Страница 11: ...Rev 4 00 Sep 14 2005 Page xi of l USB Universal serial bus WDT Watch dog timer...
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Страница 204: ...Section 4 Clock Pulse Generator CPG Rev 4 00 Sep 14 2005 Page 154 of 982 REJ09B0023 0400...
Страница 212: ...Section 5 Watchdog Timer WDT Rev 4 00 Sep 14 2005 Page 162 of 982 REJ09B0023 0400...
Страница 228: ...Section 6 Power Down Modes Rev 4 00 Sep 14 2005 Page 178 of 982 REJ09B0023 0400...
Страница 246: ...Section 8 X Y Memory Rev 4 00 Sep 14 2005 Page 196 of 982 REJ09B0023 0400...
Страница 318: ...Section 11 User Break Controller UBC Rev 4 00 Sep 14 2005 Page 268 of 982 REJ09B0023 0400...
Страница 454: ...Section 12 Bus State Controller BSC Rev 4 00 Sep 14 2005 Page 404 of 982 REJ09B0023 0400...
Страница 500: ...Section 13 Direct Memory Access Controller DMAC Rev 4 00 Sep 14 2005 Page 450 of 982 REJ09B0023 0400...
Страница 504: ...Section 14 U Memory Rev 4 00 Sep 14 2005 Page 454 of 982 REJ09B0023 0400...
Страница 566: ...Section 17 Compare Match Timer CMT Rev 4 00 Sep 14 2005 Page 516 of 982 REJ09B0023 0400...
Страница 734: ...Section 18 Multi Function Timer Pulse Unit MTU Rev 4 00 Sep 14 2005 Page 684 of 982 REJ09B0023 0400...
Страница 868: ...Section 21 A D Converter Rev 4 00 Sep 14 2005 Page 818 of 982 REJ09B0023 0400...
Страница 914: ...Section 23 I O Ports Rev 4 00 Sep 14 2005 Page 864 of 982 REJ09B0023 0400...
Страница 956: ...Section 24 List of Registers Rev 4 00 Sep 14 2005 Page 906 of 982 REJ09B0023 0400...
Страница 1016: ...Section 25 Electrical Characteristics Rev 4 00 Sep 14 2005 Page 966 of 982 REJ09B0023 0400...
Страница 1024: ...Appendix Rev 4 00 Sep 14 2005 Page 974 of 982 REJ09B0023 0400...
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