NJU6535 查看數據表（PDF） - Japan Radio Corporation
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NJU6535 Datasheet PDF : 30 Pages
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NJU6535
(6-7) Key More Input
Key scan signal output terminal S0 to S5 output “H” level in state of Key More Input. Although Key state is
detected without diodes to prevent unexpected key scan signal flow, non-pressed key data may change
pressed key data in triple or more key Input as shown in Fig. 1 and incorrect key data may be output to
external CPU. For prevention of miss-recognition by incorrect key data, diodes should be inserted in front
of K0 – K4 terminals as shown in Fig. 3 or control program of CPU should ignore the combination of key
data miss-recognition. For example, 4 keys and more ON data should be ignored.
S0
Pressed key
S1
Miss-recognized key
S2
S3
In case of 3 keys operation in left
picture, if S4 terminal outputs “H”
S4
signal, this signal goes around on
S5
the dotted line and non-pressed key
is miss-recognized as pressed
K0
key.
K1
K2
K3
K4
Fig. 1 Miss-recognized example by key more input
In modes of power save 1 (S0=0, S1=1 / Keys on only S5 line are valid) or power save 2 (S0=0, S1=1 /
Keys on only S4 and S5 lines are valid), pay attention about the followings. When Key More Input is
operated across the valid line and invalid, non-pressed key is miss-recognized as pressed key. However,
Key data on the invalid line is not read out and 4 keys and more operation in the mean time are not
ignored by CPU control program as shown in Fig. 2. In this case, diodes operate to prevent
miss-recognition as shown in Fig. 3.
S0
S1
S2
No active key
S3
S4
S5
Active key
K0
K1
K2
Pressed key
K3
K4
Miss-recognized key
In case of power save 1, CPU control program can
not decide ether correct key data or incorrect as
shown above because key data on only S4 line is
read out to CPU (all of key data on S4 line become to
“0”
Fig. 2 Miss-recognition in power save 1
S0
S1
S2
S3
S4
Miss-recognition
prevent diodes
S5
K0
K1
K2
K3
K4
Fig. 3 Connect miss-recognition prevent diodes
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