Casio IT-2000W manual ABC Auto Backlight Control

6.5Backlight Control

This terminal has incorporated two types of automatic backlight control functions: ABO (Auto Backlight OFF) and ABC (Auto Backlight Control). The ABO function is used to turn off the backlight if no key or touch panel input has been made for a given period of time, and the ABC function is used to automatically turn on and off the backlight depending on the intensity of the ambient light. These operations are performed by the keyboard controller.

ABC (Auto Backlight Control)

The ABC function automatically turns on or off the backlight by detecting the ambient light intensity. Every second it determines the amount of light received by the illumination sensor and automatically turns on or off the backlight depending on whether the amount of light is less than the given amount or more than the given amount.

Amount of Light

Backlight OFF

Light

Backlight ON

Margin to turn OFF

Margin to turn ON

Dark

Fig. 6.5

In the above graph, the marginal light amount across which the backlight is turned ON is at a setting less than if the backlight is OFF. If these two levels are identical, the backlight will flicker if it detects a small variation in the incident light on the illumination sensor. To avoid this problem an appropriate hysterisis is provided.

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