HD6412240 RENESAS [Renesas Technology Corp], HD6412240 Datasheet - Page 196

• Manufacturer Part Number: HD6412240
• Description: Renesas 16-Bit Single-Chip Microcomputer H8S Family / H8S/2200 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 6 Bus Controller
16-Bit Access Space
Figure 6.9 illustrates data alignment control for the 16-bit access space. With the 16-bit access
space, the upper data bus (D
amount of data that can be accessed at one time is one byte or one word, and a longword transfer
instruction is executed as two word transfer instructions.
In byte access, whether the upper or lower data bus is used is determined by whether the address is
even or odd. The upper data bus is used for an even address, and the lower data bus for an odd
address.
Rev.3.00 Mar. 26, 2007 Page 154 of 772
REJ09B0355-0300
Byte size
Word size
Longword size
Figure 6.9 Access Sizes and Data Alignment Control (16-Bit Access Space)
Figure 6.8 Access Sizes and Data Alignment Control (8-Bit Access Space)
Byte size
Byte size
Word size
Longword
size
• Even address
• Odd address
1st bus cycle
2nd bus cycle
15
1st bus cycle
2nd bus cycle
1st bus cycle
2nd bus cycle
3rd bus cycle
4th bus cycle
to D
8
) and lower data bus (D
D
Upper data bus
15
D
15
Upper data bus
7
to D
D
0
) are used for accesses. The
8
D
D
8
Lower data bus
7
D
7
Lower data bus
D
0
D
0