NEC V850E/RS1, Руководство пользователя, Страница: 213 / 852

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Chapter 5 Bus Control Function
User’s Manual U16702EE3V2UD00
5.4.3 Access by bus size
The V850E/RS1 accesses the on-chip peripheral I/O and external memory in 8-bit, 16-bit, or 32-bit
units. The bus size is as follows.
• The bus size of the on-chip peripheral I/O is fixed to 16 bits.
• The bus size of the external memory is selectable from 8 bits or 16 bits (by using the BSC register).
The operation when each of the above is accessed is described below. All data is accessed starting
from the lower side.
The V850E/RS1 supports only the Little-Endian format.
Figure 5-3: Little-Endian Address in Word
(1) Byte access (8 bits)
(a) 16-bit data bus width
<1> Access to even address (2n) <2> Access to odd address (2n + 1)
(b) 8-bit data bus width
<1> Access to even address (2n) <2> Access to odd address (2n + 1)
000BH 000AH 0009H 0008H
0007H 0006H 0005H 0004H
0003H 0002H 0001H 0000H
31 24 23 16 17 8 7 0
7
0
7
0
Byte data
15
8
External
data bus
2n
Address
7
0
7
0
Byte data
15
8
External
data bus
2n + 1
Address
7
0
7
0
Byte data External
data bus
2n
Address
7
0
7
0
Byte data External
data bus
2n + 1
Address
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