HD64F3048F16 Datasheet, PDF (164/903 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 6 Bus Controller
6.3.3 Data Bus
The H8/3048B Group allows either 8-bit access or 16-bit access to be designated for each of areas
7 to 0. 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
(D to D )
15
8
Valid
Lower Data Bus
(D to D )
7
0
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.
Rev. 3.00 Sep 27, 2006 page 136 of 872
REJ09B0325-0300