HT47C20 datasheet(34/56 Pages) HOLTEK

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HT47C20

January 18, 2000

Mask option

The following shows many kinds of mask options in the HT47C20. All these options should be defined

in order to ensure proper system functioning.

No.

Mask Option

OSC type selection. This option is to decide if an RC or a crystal oscillator is chosen as sys-

tem clock.

Clock source selection of WDT, RTC and Time Base. There are three types of selection: sys-

tem clock/4 or RTC OSC or WDT OSC.

WDT enable/disable selection. WDT can be enabled or disabled by mask option.

CLR WDT times selection. This option defines how to clear the WDT by instruction. One

time means that the ²CLR WDT² can clear the WDT. ²Two times² means that only if both

of the ²CLR WDT1² and ²CLR WDT2² have been executed, then WDT can be cleared.

Time Base time-out period selection. The Time Base time-out period ranges from fs/212 to

fs/215. ²fs² means the clock source selected by mask option.

Buzzer output frequency selection. There are eight types frequency signals for buzzer out-

put: fs/22~fs/29. ²fs² means the clock source selected by mask option.

Wake-up selection. This option defines the wake-up function activity. External I/O pins

(PA only) all have the capability to wake-up the chip from a halt mode by a following edge.

Pull high selection. This option is to decide whether the pull high resistance is viable or not

on the low nibble of the PA.

PA CMOS or NMOS selection.

The structure of the low nibble of the PA can be selected to be CMOS or NMOS. When the

CMOS is selected, the related pins only can be used for output operations. When the NMOS

is selected, the related pins can be used for input or output operations.

I/O pins share with other function selection.

PA0/BZ, PA1/BZ: PA0 and PA1 can be set as I/O pins or buzzer outputs.

PA2/IR: PA2 can be set as I/O pins or IR carrier output.

PA3/PFD: PA3 can be set as I/O pins or PFD output.

LCD common selection. There are two types of selection: 3 commons (1/3 duty, 1/2 bias) or 4

commons (1/4 duty, 1/3 bias). If the 4 commons is selected, the segment output pin

²SEG19/COM3² will be set as a common output ²COM3².

LCD driver clock selection. There are seven types of frequency signals for the LCD driver

circuits: fs/22~fs/28. ²fs² means the clock source selection by mask option.

LCD on or LCD off at the halt mode selection.

The LCD can be enable or disable at the halt mode by mask option.

HT47C20 Folha de dados(PDF) 34 Page - Holtek Semiconductor Inc