r4f2426 Renesas Electronics Corporation., r4f2426 Datasheet - Page 217

• Manufacturer Part Number: r4f2426
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

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.
6.5.2
Table 6.3 shows the data buses used and valid strobes for the access spaces.
In a read, the RD signal is valid for both the upper and the lower half of the data bus. In a write,
the HWR signal is valid for the upper half of the data bus, and the LWR signal for the lower half.
Table 6.3
Note: Hi-Z: High-impedance state
Area
8-bit access
space
16-bit access
space
Invalid: Input state; input value is ignored.
Figure 6.9 Access Sizes and Data Alignment Control (16-Bit Access Space)
Valid Strobes
Byte size
Byte size
Word size
Longword
size
Data Buses Used and Valid Strobes
Access
Size
Byte
Byte
Word
• Even address
• Odd address
1st bus cycle
2nd bus cycle
Read/
Write
Read
Write
Read
Write
Read
Write
Address


Even
Odd
Even
Odd


D15
Upper data bus
Valid
Strobe
RD
HWR
RD
HWR
LWR
RD
HWR, LWR
Rev. 1.00 Sep. 19, 2008 Page 189 of 1270
D8 D7
Upper Data Bus
(D15 to D8)
Valid
Valid
Invalid
Valid
Hi-Z
Valid
Valid
Lower data bus
Section 6 Bus Controller (BSC)
Lower Data
Bus (D7 to D0)
Invalid
Hi-Z
Invalid
Valid
Hi-Z
Valid
Valid
Valid
REJ09B0466-0100
D0