Analog Devices SHARC ADSP-214 Series Hardware Reference Manual page 696

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Functional Description

interrupt is enabled, the RTC generates an interrupt on the day and time

specified. The alarm interrupt and day alarm interrupt can be enabled or

disabled independently.

The RTC provides a stopwatch function that acts as a countdown timer.

The application can program a second count into the RTC Stopwatch

Count register (

the specified number of seconds have elapsed, the RTC generates an

To guard against the possibility of long term (> 1 day) errors, the RTC

provides a calibration feature using 4 bits of the

available for the stopwatch function).

This is a simple a time correction at the end of every day (when the clock

YYY:00:00:00). It functions by adding or subtracting an integer number

of seconds (maximum of 7) from the start of the next day, to correct accu-

mulated time error over the course of the previous day. The number of

seconds that are added or subtracted is defined in the

As an example, if there is a –50 ppm error in the 1Hz frequency, this

translates into 86400 × 50 ppm seconds (=+4.32 seconds) error at the end

of the day. That is at 00:00:00, RTC time is 4.32 seconds ahead of actual

time. The RTC can correct this by adding 4 seconds (if 4 is the value writ-

ten into the calibration register) to the time at 00:00:00. Therefore, from

23:59:59, the timer counter jumps directly to 00:00:04, (there is no

00:00:00 to 00:00:03 time occurances). At the instant it jumps to

00:00:04, the error reduces to +0.32 seconds over the course of the day,

which is only 3.7 ppm.

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). When the stopwatch interrupt is enabled and

ADSP-214xx SHARC Processor Hardware Reference

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