170
7.4.5
Wait Control
When accessing external space, the H8S/2633 Series 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. 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 ø 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.
Содержание H8S/2631
Страница 28: ...xviii Appendix G Package Dimensions 1154 ...
Страница 341: ...316 Transfer SAR or DAR DAR or SAR Block area First block Nth block Figure 9 8 Memory Mapping in Block Transfer Mode ...
Страница 918: ...905 ø DREQ0 DREQ1 tDRQS tDRQH Figure 25 19 DMAC DREQ Input Timing ...
Страница 955: ...943 A 2 Instruction Codes Table A 2 shows the instruction codes ...