NJU6538 View Datasheet(PDF) - Japan Radio Corporation

Part Name

Description

Manufacturer

NJU6538

1/8, 1/9, 1/10 Duty BITMAP LCD DRIVER with KEY SCAN

Japan Radio Corporation  

NJU6538

(5-8) Key data reading out operation by external MPU

(a) Display data writing

Display data and an instruction change operate at the rising edge of 9-bit on SCL signal.

(b) Key data reading out operation

The minimum period from Key in to SIO terminal = “L” is 322T(t1) by key scan operation. When

key scan operation performs again for key data fix preventing from noise or bouncing of key, the

period from Key in to SIO terminal = “L” is 676T(t1). When the SIO terminal outputs “L”, the key

scan operation is stopped after execution of key data reading out operation. Therefore, fixed key

data is kept until end of key data reading out operation. When key data reading out operation is

performed during SO terminal = “H”, both of key data from KD1 to KD25 and power save flag (PSF)

are not outputted correctly.

Key data reading out operation example

The flowchart below shows an example of timer interrupt application. When SIO terminal

condition is “L” after check of SIO terminal condition at every timer interrupt operation, it is decided

as Key In and key data reading out operation is performed. When SIO terminal condition is “H, it is

decided as Key Off. For the correct decision of Key Off, the timer interrupt cycle (1/t3) should be

expanded over the time added with [period of key scan (676T in case of measure against key

bouncing of key) and [period of key data reading out operation (t2)]. In this time, the period of timer

interrupt cycle (t3) must be set with enough margins including the range of fosc.

Sequence of key data reading out operation

Timer

Yes

SO=”L”?

No

Key ON

Key OFF

Key data

read out

End of Timer

Ver.2003-05-09

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