HD6413002 Datasheet, PDF (130/700 Pages) Renesas Technology Corp – High-performance single-chip microcontroller

6.3.3 Data Bus
The H8/3002 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 (D₁₅ to D₈). A 16-bit-access area uses both the upper
data bus (D₁₅ to D₈) and lower data bus (D₇ to D₀).
In read access the RD signal applies without distinction to both the upper and lower data bus. In
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
Access Read/
Size Write
—
Read
Write
Valid
Address Strobe
—
RD
—
HWR
Upper Data Bus
(D₁₅ to D₈)
Valid
Lower Data Bus
(D₇ to D₀)
Invalid
Undetermined data
16-bit-access Byte
Read Even
RD
area
Odd
Valid
Invalid
Invalid
Valid
Write Even
HWR
Valid
Undetermined data
Odd
LWR
Undetermined data Valid
Word Read —
RD
Valid
Valid
Write —
HWR, LWR Valid
Valid
Note: Undetermined data means that unpredictable data is output.
Invalid means that the bus is in the input state and the input is ignored.
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