NJU6535 データシートの表示（PDF） - Japan Radio Corporation

部品番号

コンポーネント説明

メーカー

NJU6535

1/3 , 1/4 Duty LCD Driver

Japan Radio Corporation  

NJU6535

(6-6) Power save mode

Key scan operates with follows in Power save mode.

1, Key scan signal output terminals S0 – S5 output “H”, “L” signals by the control data S0 and S1 when key scan does not

operate (refer the detail of instructions), and output key scan signals after start of key scan operation. The conditions of

key scan signal input terminals K0 – K4 are “L” state with internal pull-down resistances, though “H” signal comes in to K0

– K4 corresponding to the turned on keys.

2, The oscillation circuit function of key scan starts twice operations when any keys on cross points with S0– S5 terminals

line and K0 – Ki turned on. It stops when a couple of data by continuously twice key scan operations are accorded and

fixed as a correct key status. It operates more 2 times when the key status is not fixed and any keys are still turning on. It

repeats again and again until key status is fixed. The correct key status data is stored and newly key scan operation does

not start until external CPU reads data out after key status is fixed.

3, When the key status is fixed, SO terminal outputs “L” signal as Key data read out request to CPU. CPU should read key

data out at detection of this “L” signal. If CPU writes the display data or instructions to the NJU6535 when SO terminal

outputs “L” signal, SO terminal outputs “H” level during “CE” terminal is ”H”.

4, The Key data read out request signal is released and SO terminal outputs “H” signal after finish of CPU key data read

out for newly key scan operation. Although Power save mode is not released.

SO terminal requires pull up resistor (1Kohm to 10Kohms) because of Open drain type output. Multiple data of key are

output in case of key more input so that CPU should process the data by itself.

Key scan example (Power save mode)

Ex.) PS0= ”0”, PS1= ”1” (K4=“H” power save)

S0 “L”

S1 “L”

S2 “L”

S3 “L”

S4 “L”

S5 “H”

K0

K1

K2

K3

K4

When some key on these lines are turned on, the

oscillation starts and Key scan starts the operation until all

of key are turned off.

*1

*1 These diodes are required to recognize key more input of keys on the K4 line when only K4 terminal outputs “H”

signal in power save mode as shown above example. In case of no diodes, incorrect key data may read out

sometimes by key more input of keys on lines of K0 to K4.

Key input

(K4)

Key scan

CE

577T[s]

577T[s]

SCL

SI

Data send

Data send

Data send

T = 1 / fosc

SO

Key data read

Key data read

Key data read

request

Key data read

request

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