¡ Semiconductor
MSM9223
Keyscan
Keyscanning is started only when depression or release of any key is detected in order to
minimize noise caused by scanning signal. Then, keyscanning is continued until the keyscan
stop mode is sent from a microcomputer. The INT pin goes to the high level at the completion
of 1-cycle scanning after the keyscan start, so the (high level) signal sent from the INT pin can be
used as an interrupt signal.
[Keyscan Timing]
ROW 0
ROW 1
ROW 2
ROW 3
ROW 4
INT
1 Cycle
Depress/Release
Keyscan stop mode
is selected.
Note:
Keyscanning cannot be stopped by selecting the keyscan stop mode only once if:
- keyscanning is started after depression or release of any key is detected, and then
- a key is depressed or released again before the keyscan stop mode is selected.
To stop keyscanning, it is required to select the keyscan stop mode once again.
Depress
Depress
INT
Keyscan
CS
MODE5
MODE5 : Keyscan stop
Release
Keyscan
MODE5
MODE5
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