STK17TA8

February 2004

18

Document Control # ML0023 rev 0.3

1FFFCh

Timekeeping - Day

D7

D6

D5

D4

D3

D2

D1

D0

XXX

XX

Day of Week

Lower nibble contains a value that correlates to day of the week. Day of the week is a ring counter that counts from 1 to 7 then returns to 1.

The user must assign meanting to the day value, as the day is not integrated with the date.

1FFFBh

Timekeeping - Hours

D7

D6

D5

D4

D3

D2

D1

D0

12/24

X

10s Hours

Hours

Contains the BCD value of hours in 24 hour format. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble (two bits)

contains the upper digit and operates from 0 to 2. The range for the register is 0-23.

1FFFAh

Timekeeping - Minutes

D7

D6

D5

D4

D3

D2

D1

D0

X

10s Minutes

Minutes

Contains the BCD value of minutes. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble contains the upper min-

utes digit and operates from 0 to 5. The range for the register is 0-59.

1FFF9h

Timekeeping - Seconds

D7

D6

D5

D4

D3

D2

D1

D0

X

10s Seconds

Seconds

Contains the BCD value of seconds. Lower nibble contains the lower digit and operates from 0 to 9; upper nibble contains the upper digit

and operates from 0 to 5. The range for the register is 0-59.

1FFF8h

Contol/Calibration

D7

D6

D5

D4

D3

D2

D1

D0

OSCEN

X

Calibration

Sign

Calibration

OSCEN

Oscillator Enable. When set to 1, the oscillator is halted. When set to 0, the oscillator runs. Disabling the oscillator saves battery/capacitor

power during storage. On a no-battery power-up, this bit is set to 1. The RTC will not run until the oscillator is enabled. Set this bit to 0 to

activate the RTC.

Calibration Sign

Determines if the calibration adjustment is applied as an addition to or as a subtraction from the time-base.

Calibration

These five bits control the calibration of the clock.

1FFF7h

Watchdog Timer

D7

D6

D5

D4

D3

D2

D1

D0

WDS

WDW

WDT

WDS

Watchdog Strobe. Setting this bit to 1 reloads and restarts the watchdog timer. Setting the bit to 0 has no affect. The bit is cleared automat-

ically once the watchdog timer is reset. The WDS bit is write only. Reading it always will return a 0.

WDW

Watchdog Write Enable. Setting this bit to 1 masks the watchdog timeout value (WDT5-WDT0) so it cannot be written. This allows the user

to strobe the watchdg without disturbing the timeout value. Setting this bit to 0 allows bits 5-0 to be witten on the next write to the Watchdog

register. The new value will be loaded on the nex internal watchdog clock after the write cycle is complete. This function is explained in

more detail in the watchdog timer section.