DF2211NP24V Renesas Technology / Hitachi Semiconductor, DF2211NP24V Datasheet - Page 188

• Manufacturer Part Number: DF2211NP24V
• Description: H8S/2200 Series, 2212 Group, USB, RTC, HSS TNP-64B; Vcc= 2.7 to 3.6 volts, Temp= -20 to 75 C; Package: PVQN0064LB-A
• Manufacturer: Renesas Technology / Hitachi Semiconductor

6.6
The basic bus interface enables direct connection of ROM, SRAM, and so on.
6.6.1
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 (D15 to D8) or lower data bus (D7 to D0) is used according to the bus
specifications for the area being accessed (8-bit access space or 16-bit access space) and the data
size.
8-Bit Access Space: Figure 6.8 illustrates data alignment control for the 8-bit access space. With
the 8-bit access space, the upper data bus (D15 to D8) is always used for accesses. The amount of
data that can be accessed at one time is one byte: a word transfer instruction is performed as two-
byte accesses, and a longword transfer instruction, as four-byte accesses.
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 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.7.00 Dec. 24, 2008 Page 134 of 698
REJ09B0074-0700
Basic Bus Interface
Data Size and Data Alignment (Supported Only by the H8S/2218 Group)
Figure 6.8 Access Sizes and Data Alignment Control (8-Bit Access Space)
Byte size
Word size
Longword
size
1st bus cycle
2nd bus cycle
1st bus cycle
2nd bus cycle
3rd bus cycle
4th bus cycle
D15
Upper data bus
D8 D7
Lower data bus
D0