Renesas H8S/2318 series, Руководство по оборудованию

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Rev. 5.00, 12/03, page 168 of 1088
6.4.5 Wait Control
When accessing external space, the H8S/2319 and H8S/2318 Groups can extend the bus cycle by
inserting one or more wait states (T
w
). There are two ways of inserting wait states: program wait
insertion and pin wait insertion using the
WAIT
pin.
Program Wait Insertion: From 0 to 3 wait states can be inserted automatically between the T
2
state and T
3
state on an individual area basis in 3-state access space, according to the settings of
WCRH and WCRL.
Pin Wait Insertion: Setting the WAITE bit in BCRL to 1 enables wait insertion by means of the
WAIT
pin. When external space is accessed in this state, program wait insertion is first carried out
according to the settings in WCRH and WCRL. Then, if the
WAIT
pin is low at the falling edge of
φ
in the last T
2
or T
w
state, a T
w
state is inserted. If the
WAIT
pin is held low, T
w
states are
inserted until it goes high.
This is useful when inserting four or more T
w
states, or when changing the number of T
w
states for
different external devices.
The WAITE bit setting applies to all areas.