Datasheet

Section 6 Bus Controller (BSC)
R01UH0309EJ0500 Rev. 5.00 Page 195 of 1408
Sep 24, 2012
H8S/2456, H8S/2456R, H8S/2454 Group
(2) 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 (D15 to D8) and lower data bus (D7 to D0) are used for accesses. The
amount of data that can be accessed at one time is one byte or one word, and a longword access is
executed as two word accesses.
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.
D15 D8 D7 D0
Upper data bus Lower data bus
Byte size
Word size
1st bus cycle
2nd bus cycle
Longword
size
• Even address
Byte size
• Odd address
Figure 6.9 Access Sizes and Data Alignment Control (16-Bit Access Space)