HD6433044 Hitachi Semiconductor, HD6433044 Datasheet - Page 138

• Manufacturer Part Number: HD6433044
• Description: (HD64 Series) Hitachi Single-Chip Microcomputer
• Manufacturer: Hitachi Semiconductor

6.3.3 Data Bus
The H8/3048 Series allows either 8-bit access or 16-bit access to be designated for each of
areas 0 to 7. An 8-bit-access area uses the upper data bus (D
both the upper data bus (D
In read access the
write access the HWR signal applies to the upper data bus, and the LWR signal applies to the
lower data bus.
Table 6-4 indicates how the two parts of the data bus are used under different access conditions.
Table 6-4 Access Conditions and Data Bus Usage
Area
8-bit-access
area
16-bit-access
area
Note: Undetermined data means that unpredictable data is output.
Invalid means that the bus is in the input state and the input is ignored.
Access Read/
Size
—
Byte
Word
RD signal applies without distinction to both the upper and lower data bus. In
Write
Read
Write
Read
Write
Read
Write
15
to D
8
Address Strobe
—
—
Even
Odd
Even
Odd
—
—
) and lower data bus (D
Valid
RD
HWR
RD
HWR
LWR
RD
HWR, LWR Valid
124
Upper Data Bus
(D
Valid
Valid
Invalid
Valid
Undetermined data Valid
Valid
7
to D
15
15
to D
to D
0
).
8
8
)
). A 16-bit-access area uses
Lower Data Bus
(D
Invalid
Undetermined data
Invalid
Valid
Undetermined data
Valid
Valid
7
to D
0
)