NJU6535FH1 NJR, NJU6535FH1 Datasheet - Page 16

• Manufacturer Part Number: NJU6535FH1
• Description: LCD Drivers 1/3 1/4 LCD
• Manufacturer: NJR

Specifications of NJU6535FH1

• Operating Supply Voltage: 5.5 V
• Maximum Operating Temperature: + 70 C
• Package / Case: PQFP-H1
• Minimum Operating Temperature: 0 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

NJU6535
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(6-7) Key More Input
S0
S1
S2
S3
S4
S5
K0
K1
K2
K3
K4
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
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.
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.
Key scan signal output terminal S0 to S5 output “H” level in state of Key More Input. Although Key state is
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 /
S0
S1
S2
S3
S4
S5
K0
K1
K2
K3
K4
power save 1
Fig. 1
No active key
Active key
Pressed key
Miss-recognized key
Miss-recognized example by
In case of 3 keys operation in left
picture, if S4 terminal outputs “H”
signal, this signal goes around on
the dotted line and non-pressed key
is
key.
Pressed key
Miss-recognized key
miss-recognized
S0
S1
S2
S3
S4
S5
K0
K1
K2
K3
K4
Fig. 3 Connect miss-recognition prevent diodes
key more input
as
pressed
Miss-recognition
prevent diodes
Ver.2004-04-16