HT46R01A datasheet(40/58 Pages) HOLTEK

40 / 58 page

HT46R01A

Rev. 1.10

August 13, 2008

Under normal program operation, a Watchdog Timer

time-out will initialise a device reset and set the status bit

TO. However, if the system is in the Power Down Mode,

when a Watchdog Timer time-out occurs, the device will

be woken up, the TO bit in the status register will be set

and only the Program Counter and Stack Pointer will be

reset. Three methods can be adopted to clear the con-

tents of the Watchdog Timer. The first is an external

hardware reset, which means a low level on the external

reset pin, the second is using the Clear Watchdog Timer

software instructions and the third is when a HALT in-

struction is executed. There are two methods of using

software instructions to clear the Watchdog Timer, one

of which must be chosen by configuration option. The

first option is to use the single

²CLR WDT² instruction

while the second is to use the two commands

²CLR

WDT1

² and ²CLR WDT2². For the first option, a simple

execution of

²CLR WDT² will clear the Watchdog Timer

while for the second option, both

²CLR WDT1² and

²CLR WDT2² must both be executed to successfully

clear the Watchdog Timer. Note that for this second op-

tion, if

²CLR WDT1² is used to clear the Watchdog

Timer, successive executions of this instruction will

have no effect, only the execution of a

²CLR WDT2² in-

struction will clear the Watchdog Timer. Similarly after

the

²CLR WDT2² instruction has been executed, only a

successive

²CLR WDT1² instruction can clear the

Watchdog Timer.

C T R L 1 R e g i s t e r

b 7

b 0

I N T E S 1

W D T E N 3

I N T E S 0

W D T E N 2 W D T E N 1 W D T E N 0

W a t c h d o g T i m e r F u n c t i o n

D i s a b l e

E n a b l e - r e c o m m e n d e d v a l u e

O t h e r v a l u e s - a l l e n a b l e

W S 2

W D T S R e g i s t e r

b 7

b 0

W D T p r e s c a l e r r a t e s e l e c t

W S 2

W S 1

W S 0

W D T R a t e

1 : 1

1 : 2

1 : 4

1 : 8

1 : 1 6

1 : 3 2

1 : 6 4

1 : 1 2 8

N o t u s e d

W S 1 W S 0

Configuration Options

Configuration options refer to certain options within the MCU that are programmed into the OTP Program Memory de-

vice during the programming process. During the development process, these options are selected using the HT-IDE

software development tools. As these options are programmed into the device using the hardware programming tools,

once they are selected they cannot be changed later by the application software. All options must be defined for proper

system function, the details of which are shown in the table.

No.

Options

Watchdog Timer: enable or disable

Watchdog Timer clock source: WDT internal oscillator, fSYS/4 or RTC

CLRWDT instructions: 1 or 2 instructions

System oscillator: Internal RC, Internal RC with external RTC, External Crystal, External RC

LVR function: enable or disable

LVR voltage: 2.1V, 3.15V or 4.2V

RES or PA7

SST: enable (1024 clocks) or disable (2 clocks)

HT46R01A Datasheet(PDF) 40 Page - Holtek Semiconductor Inc

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