
Section 12 Bus State Controller (BSC)
Rev. 4.00 Sep. 14, 2005 Page 351 of 982
REJ09B0023-0400
Burst Read: A burst read occurs in the following cases with this LSI.
•
Access size in reading is larger than data bus width.
•
16-byte transfer in cache error.
•
16-byte transfer in DMAC
This LSI always accesses the SDRAM with burst length 1. For example, read access of burst
length 1 is performed consecutively 4 times to read 16-byte continuous data from the SDRAM that
is connected to a 32-bit data bus.
Table 12.14 shows the relationship between the access size and the number of bursts.
Table 12.14 Relationship between Access Size and Number of Bursts
Bus Width
Access Size
Number of Bursts
16 bits
8 bits
1
16
bits
1
32
bits
2
16
bits
8
32 bits
8 bits
1
16
bits
1
32
bits
1
16
bits
4
Figures 12.18 and 12.19 show a timing chart in burst read. In burst read, an ACTV command is
output in the Tr cycle, the READ command is issued in the Tc1, Tc2, and Tc3 cycles, the READA
command is issued in the Tc4 cycle, and the read data is received at the rising edge of the external
clock (CKIO) in the Td1 to Td4 cycles. The Tap cycle is used to wait for the completion of an
auto-precharge induced by the READA command in the SDRAM. In the Tap cycle, a new
command will not be issued to the same bank. However, access to another CS space or another
bank in the same SDRAM space is enabled. The number of Tap cycles is specified by the WTRP1
and WTRP0 bits in the CS3WCR register.
In this LSI, wait cycles can be inserted by specifying each bit in the CS3WCR register to connect
the SDRAM in variable frequencies. Figure 12.19 shows an example in which wait cycles are
inserted. The number of cycles from the Tr cycle where the ACTV command is output to the Tc1
cycle where the READ command is output can be specified using the WTRCD1 and WTRCD0
bits in the CS3WCR register. If the WTRCD1 and WTRCD0 bits specify one cycles or more, a
Trw cycle where the NOT command is issued is inserted between the Tr cycle and Tc1 cycle. The
Summary of Contents for HD6417641
Page 2: ...Rev 4 00 Sep 14 2005 Page ii of l...
Page 7: ...Rev 4 00 Sep 14 2005 Page vii of l...
Page 11: ...Rev 4 00 Sep 14 2005 Page xi of l USB Universal serial bus WDT Watch dog timer...
Page 12: ...Rev 4 00 Sep 14 2005 Page xii of l...
Page 28: ...Rev 4 00 Sep 14 2005 Page xxviii of l...
Page 204: ...Section 4 Clock Pulse Generator CPG Rev 4 00 Sep 14 2005 Page 154 of 982 REJ09B0023 0400...
Page 212: ...Section 5 Watchdog Timer WDT Rev 4 00 Sep 14 2005 Page 162 of 982 REJ09B0023 0400...
Page 228: ...Section 6 Power Down Modes Rev 4 00 Sep 14 2005 Page 178 of 982 REJ09B0023 0400...
Page 246: ...Section 8 X Y Memory Rev 4 00 Sep 14 2005 Page 196 of 982 REJ09B0023 0400...
Page 318: ...Section 11 User Break Controller UBC Rev 4 00 Sep 14 2005 Page 268 of 982 REJ09B0023 0400...
Page 454: ...Section 12 Bus State Controller BSC Rev 4 00 Sep 14 2005 Page 404 of 982 REJ09B0023 0400...
Page 504: ...Section 14 U Memory Rev 4 00 Sep 14 2005 Page 454 of 982 REJ09B0023 0400...
Page 566: ...Section 17 Compare Match Timer CMT Rev 4 00 Sep 14 2005 Page 516 of 982 REJ09B0023 0400...
Page 868: ...Section 21 A D Converter Rev 4 00 Sep 14 2005 Page 818 of 982 REJ09B0023 0400...
Page 914: ...Section 23 I O Ports Rev 4 00 Sep 14 2005 Page 864 of 982 REJ09B0023 0400...
Page 956: ...Section 24 List of Registers Rev 4 00 Sep 14 2005 Page 906 of 982 REJ09B0023 0400...
Page 1016: ...Section 25 Electrical Characteristics Rev 4 00 Sep 14 2005 Page 966 of 982 REJ09B0023 0400...
Page 1024: ...Appendix Rev 4 00 Sep 14 2005 Page 974 of 982 REJ09B0023 0400...
Page 1032: ...Rev 4 00 Sep 14 2005 Page 982 of 982 REJ09B0023 0400 X X Y data addressing 52 X Y memory 193...
Page 1035: ......
Page 1036: ...SH7641 Hardware Manual...