6.4.3
Valid Strobes
Table 6-4 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 6-4
Data Buses Used and Valid Strobes
Access
Area
Size
8-bit access
Byte
space
16-bit access
Byte
space
Word
Notes: Hi-Z: High impedance
Invalid: Input state; input value is ignored.
Read/
Valid
Write
Address
Strobe
RD
Read
—
HWR
Write
—
RD
Read
Even
Odd
HWR
Write
Even
LWR
Odd
RD
Read
—
HWR, LWR Valid
Write
—
Upper Data Bus
Lower Data Bus
(D
to D
)
(D
15
8
Valid
Invalid
Hi-Z
Valid
Invalid
Invalid
Valid
Valid
Hi-Z
Hi-Z
Valid
Valid
Valid
Valid
Rev. 5.00, 12/03, page 159 of 1088
to D
)
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