upd70f3017ay Renesas Electronics Corporation., upd70f3017ay Datasheet - Page 91

• Manufacturer Part Number: upd70f3017ay
• Description: V850/sa1tm 32-/16-bit Single-chip Microcontroller
• Manufacturer: Renesas Electronics Corporation.

4.3.2 Bus width
following shows the operation for each access.
(1) Byte access (8 bits)
(2) Halfword access (16 bits)
(3) Word access (32 bits)
The CPU carries out peripheral I/O access and external memory access in 8-bit, 16-bit, or 32-bit units. The
Byte access is divided into two types, access to even addresses and access to odd addresses.
In halfword access to external memory, data is dealt with as is because the data bus is fixed to 16 bits.
In word access to external memory, the lower halfword is accessed first and then the higher halfword is accessed.
(a) Access to even address
7
0
Byte data
31
16
15
0
Word data
External data bus
First
15
8
7
0
External data bus
15
CHAPTER 4 BUS CONTROL FUNCTION
0
Figure 4-2. Halfword Access (16 Bits)
Figure 4-3. Word Access (32 Bits)
Figure 4-1. Byte Access (8 Bits)
Halfword data
15
0
User’s Manual U12768EJ4V1UD
External data bus
15
0
31
16
15
0
Word data
(b) Access to odd address
7
0
Byte data
Second
External data bus
15
0
External data bus
15
7
0
8
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