SH7615 Datasheet, PDF (317/925 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperH
RISC engine Family/SH7600 Series

7.3 Access Size and Data Alignment
7.3.1 Connection to Ordinary Devices
Byte, word, and longword are supported as access units. Data is aligned based on the data width of
the device. Therefore, reading longword data from a byte-width device requires four read
operations. The bus state controller automatically converts data alignment and data length between
interfaces. An 8-bit, 16-bit, or 32-bit external device data width can be connected by using the
mode pins for the CS0 space, or by setting BCR2 for the CS1 to CS4 spaces. However, the data
width of devices connected to the respective spaces is specified statically, and the data width
cannot be changed for each access cycle. Figures 7.2 to 7.4 show the relationship between device
data widths and access units.
32-bit external device (ordinary)
A24–A0 ^D31
000000 7
000001
000002
000003
000000 15
000002
000000 31
D23
0
7
87
24 23
D15
0
7
0
15
16 15
D7
0
7
87
87
D0 _{Data input/output pin}
Byte read/write of address 0
Byte read/write of address 1
Byte read/write of address 2
0 Byte read/write of address 3
Word read/write of address 0
0 Word read/write of address 2
0 Longword read/write of address 0
Figure 7.2 32-Bit External Devices and Their Access Units
16-bit external device (ordinary)
A24–A0 ^D15
000000 7
000001
000002 7
000003
000000 15
000002 15
000000 31
000002 15
D7
0
7
0
7
D0 _{Data input/output pin}
Byte read/write of address 0
0 Byte read/write of address 1
Byte read/write of address 2
0 Byte read/write of address 3
0 Word read/write of address 0
0 Word read/write of address 2
16
0 Longword read/write of address 0
Figure 7.3 16-Bit External Devices and Their Access Units
Rev. 2.00, 03/05, page 279 of 884