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Section 6 Bus Controller (BSC)
(1)
8-Bit Access Space
With the 8-bit access space, the lower byte data bus (D7 to D0) is always used for access. The
amount of data that can be accessed at one time is one byte: a word access is performed as two
byte accesses, and a longword access, as four byte accesses.
Figures 6.10 and 6.11 illustrate data alignment control for the 8-bit access space. Figure 6.10
shows the data alignment when the data endian format is specified as big endian. Figure 6.11
shows the data alignment when the data endian format is specified as little endian.
Data
Access
Size
Address
Byte
Word
Longword
Figure 6.10 Access Sizes and Data Alignment Control for 8-Bit Access Space (Big Endian)
Access
Data
Address
Size
Byte
Word
Longword
Figure 6.11 Access Sizes and Data Alignment Control for 8-Bit Access Space
Rev.2.00 Jun. 28, 2007 Page 164 of 666
REJ09B0311-0200
Bus
Access
Cycle
Count
n
1
1st
1st
n
2
2nd
n
1st
4
2nd
3rd
4th
Bus
Access
Cycle
Count
n
1
1st
1st
n
2
2nd
n
1st
4
2nd
3rd
4th
(Little Endian)
Data Size
Byte
Byte
Byte
Byte
Byte
Byte
Byte
Data Size
Byte
Byte
Byte
Byte
Byte
Byte
Byte
Strobe signal
LHWR/LUB
LLWR/LLB
RD
Data bus
D15
D8 D7
D0
7
0
15
8
7
0
31
24
23
16
15
8
7
0
Strobe signal
LHWR/LUB
LLWR/LLB
RD
Data bus
D15
D8 D7
D0
7
0
7
0
8
15
7
0
15
8
23
16
31
24
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