HD6413008F RENESAS [Renesas Technology Corp], HD6413008F Datasheet - Page 166

• Manufacturer Part Number: HD6413008F
• Description: Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Series
• Manufacturer: RENESAS [Renesas Technology Corp]

6. Bus Controller
6.4
6.4.1
The basic bus interface enables direct connection of ROM, SRAM, and so on.
The bus specifications can be selected with ABWCR, ASTCR, WCRH, and WCRL
(see table 6.3).
6.4.2
Data sizes for the CPU and other internal bus masters are byte, word, and longword. The bus
controller has a data alignment function, and when accessing external space, controls whether the
upper data bus (D
for the area being accessed (8-bit access area or 16-bit access area) and the data size.
8-Bit Access Areas: Figure 6.7 illustrates data alignment control for 8-bit access space. With 8-bit
access space, the upper data bus (D
can be accessed at one time is one byte: a word access is performed as two byte accesses, and a
longword access, as four byte accesses.
16-Bit Access Areas: Figure 6.8 illustrates data alignment control for 16-bit access areas. With
16-bit access areas, the upper data bus (D
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.
Rev.4.00 Aug. 20, 2007 Page 122 of 638
REJ09B0395-0400
Byte size
Word size
Longword size
Basic Bus Interface
Overview
Data Size and Data Alignment
Figure 6.7 Access Sizes and Data Alignment Control (8-Bit Access Area)
15
to D
8
) or lower data bus (D
1st bus cycle
2nd bus cycle
1st bus cycle
2nd bus cycle
3rd bus cycle
4th bus cycle
15
to D
15
8
) is always used for accesses. The amount of data that
to D
7
8
to D
) and lower data bus (D
D
15
Upper data bus
0
) is used according to the bus specifications
D
8
D
7
7
Lower data bus
to D
0
) are used for
D
0