Rev. 1.00, 09/03, page 127 of 704
2. Pin Wait Mode
When accessing the external address space, a specified number of wait states T
DOW
can be
inserted between the T
4
state and T
5
state of data state. If the
WAIT
pin is low at the falling
edge of
φ
in the last T
4
or T
DOW
state, another T
DOW
state is inserted. If the
WAIT
pin is held low,
T
DOW
states are inserted until it goes high.
Pin wait mode is useful when inserting four or more T
DOW
states, or when changing the number
of T
DOW
states to be inserted for each external device.
3. Pin Auto-Wait Mode
A specified number of wait states T
DOW
are inserted between the T
4
state and T
5
state when
accessing the external address space if the
WAIT
pin is low at the falling edge of
φ
in the last
T
4
state. The number of wait states T
DOW
is specified by the settings of the WCn1 and WCn0
bits. Even if the
WAIT
pin is held low, T
DOW
states are inserted only up to the specified number
of states.
Pin auto-wait mode enables the low-speed memory interface only by inputting the chip select
signal to the
WAIT
pin.
Figure 6.26 shows an example of wait state insertion timing in pin wait mode.
Read Cycle
Data
Data
Write Cycle
T
5
T
DSW
T
DOW
T
DOW
T
3
T
4
T
5
T
DSW
T
DOW
T
DOW
T
3
T
4
AD7 to AD0
Data
Data
Data
Data
AD15 to AD8
φ
Note: n = 1 to 3
Figure 6.26 Example of Wait State Insertion Timing (Multiplex Extended Mode)
Содержание H8S/2437
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