Holtek HT827A0 Manual page 27

Mask option
The following table illustrates 5 kinds of mask option in the HT827A0. All of them have to be defined
to ensure a proper functioning system.
No.
OSC type selection
1 This option determines the selection of a system clock, whether an RC or crystal type of
oscillator.
WDT source selection
2 Three selections are provided, namely, on-chip RC oscillator, instruction clock and WDT
disable.
CLRWDT times selection
This option defines clearing WDT by instructions. ²Once² means ²CLR WDT² can clear
3
WDT. ²Twice² means WDT can be cleared only if both ²CLR WDT1² and ²CLR WDT2² are
executed.
Wake-up selection
4 This option defines the activity of the wake-up function. All of the external I/O pins (PA
only) are capable of waking up the chip from a HALT mode.
Pull-high selection
5 This option determines whether or not the pull-high resistance exists in the input mode of
the I/O ports. Each bit of the I/O port can be independently selected.
Mask Option
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HT827A0
March 15, 2000