HD64F2149 Datasheet, PDF (179/1035 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

6.4.3 Valid Strobes
Table 6.5 shows the data buses used and valid strobes for the access spaces.
In a read, the RD signal is valid without discrimination between the upper and lower halves 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 6.5 Data Buses Used and Valid Strobes
Area
Access Read/
Valid
Size Write Address Strobe
Upper Data Bus Lower Data Bus
(D15 to D8)
(D7 to D0)
8-bit access Byte
space
Read —
Write —
RD
HWR
Valid
Port, etc.
Port, etc.
16-bit access Byte Read Even
RD
space
Odd
Valid
Invalid
Invalid
Valid
Write Even
HWR
Valid
Undefined
Odd
LWR
Undefined
Valid
Word Read —
RD
Valid
Valid
Write —
HWR, LWR Valid
Valid
Notes: Undefined: Undefined data is output.
Invalid: Input state; input value is ignored.
Port, etc.: Pins are used as port or on-chip supporting module input/output pins, and not as
data bus pins.
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