SH7751 Group, SH7751R Group
Section 13 Bus State Controller (BSC)
R01UH0457EJ0301 Rev. 3.01
Page 393 of 1128
Sep 24, 2013
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Write data
Write data
RTCSR,
RTCNT,
RTCOR
RFCR
Figure 13.5 Writing to RTCSR, RTCNT, RTCOR, and RFCR
Reading RTCSR, RTCNT, RTCOR, and RFCR:
A 16-bit access must always be used when
reading RTCSR, RTCNT, RTCOR, or RFCR. Undefined bits are read as 0.
13.3
Operation
13.3.1
Endian/Access Size and Data Alignment
This LSI supports both big-endian mode, in which the most significant byte (MSByte) is at the 0
address end in a string of byte data, and little-endian mode, in which the least significant byte
(LSByte) is at the 0 address end. The mode is set by means of the MD5 external pin in a power-on
reset by means of the
RESET
pin, big-endian mode being set if the MD5 pin is low, and little-
endian mode if it is high.
A data bus width of 8, 16, or 32 bits can be selected for normal memory, 16 or 32 bits for DRAM,
32 bit for synchronous DRAM, and 8 or 16 bits for the PCMCIA interface. Data alignment is
carried out according to the data bus width and endian mode of each device. Accordingly, when
the data bus width is narrower than the access size, multiple bus cycles are automatically
generated to reach the access size. In this case, access is performed by automatically incrementing
addresses to the bus width. For example, when a long word access is performed at the area with an
8-bit bus width in the SRAM interface, each address is incremented one by one, and then access is
performed four times. In the 32-byte transfer, a total of 32-byte data is continuously transferred
according to the set bus width. The first access is performed on the data for which there was an
access request, and the remaining accesses are performed in 32-byte boundary data using
waparound. During these transfers, the bus is not released and refresh operation is not performed.
In this LSI, data alignment and data length conversion between the different interfaces is
performed automatically. Quadword access is used only in transfer by the DMAC.
The relationship between the endian mode, device data length, and access unit, is shown in tables
13.8 to 13.13.
Содержание SH7751 Group
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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 ...
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