169
7.4.5
Wait Control
When accessing external space, the H8S/2646 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.
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 input by means of the
WAIT
pin. When external space is accessed in this state, a program wait is first inserted in
accordance with the settings in WCRH and WCRL. If the
WAIT
pin is low at the falling edge of ø
in the last T
2
or T
w
state, another 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/2645
Страница 4: ......
Страница 16: ......
Страница 58: ...26 ...
Страница 110: ...78 ...
Страница 120: ...88 ...
Страница 132: ...100 ...
Страница 160: ...128 ...
Страница 172: ...140 ...
Страница 235: ...203 Transfer SAR or DAR DAR or SAR Block area First block Nth block Figure 8 8 Memory Mapping in Block Transfer Mode ...
Страница 418: ...386 ...
Страница 444: ...412 ...
Страница 530: ...498 ...
Страница 562: ...530 ...
Страница 642: ...610 ...
Страница 662: ...630 ...
Страница 688: ...656 ...
Страница 756: ...724 ...
Страница 784: ...752 ...
Страница 812: ...780 ...
Страница 837: ...805 A 2 Instruction Codes Table A 2 shows the instruction codes ...
Страница 1152: ...1120 ...