Acrosser AR-B1320 - Manual (Page 32)

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3.14 LED INDICATOR (LED1 & LED2)
AR-B1320 provides 2 on-board LEDs; one is power LED and the other is user-defined status LED.
Both LEDs are located at the right-hand corner of the board next to the CN2 floppy connector.
3.14.1 POWER LED (LED1)
This LED indicates if the VCC(+5V) power is supplied or not.
3.14.2 STATUS LED (LED2)
This LED is designed for the user to define. The LED is driven by the square wave output pin of
the RTC chip. You can activate, inactivate, and change the flash rates just by programming the
register of the RTC chip. Use different flash rates to indicate different status or operating modes.
The I/O port address of index register is 70H and data register is 71h.
(1) Active Square Wave Output (Act_Sqw)
Mov al, 0bh
Out 70h, al
In al,71h
Or al,08h
Xchg ah,al
Mov al,0bh
Out 70h,
al
Xchg ah,al
Out 71h,al
(2) Inactive Square Wave Output
Mov al,0bh
Out 70h,al
In al,71h
And al,0f7h
Xchg ah,al
Mov al,0bh
Out 70h,al
Xchg ah,al
Out 71h,al
(3) Set Flash Rate
Mov ah,FR_Data ;Flash rate data in ah register
Mov al,0ah
Out 70h,al
In al,71h
And al,0f0h
Or ah,al
Mov al,0ah
Out 70h,al
Xchg ah,al
Out 71h,al
Act_Sqw ;Active square wave output
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