Datasheet

Section 6 Bus Controller
Rev.7.00 Dec. 24, 2008 Page 145 of 698
REJ09B0074-0700
6.6.4 Wait Control
When accessing external space, this LSI can extend the bus cycle by inserting one or more wait
states (Tw). 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 BCRH to 1 enables wait insertion by means of the
WAIT pin in the H8S/2218 Group. 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.