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©2006 Semtech Corp.

SH3003

www.semtech.com

Not authorized for release outside of Semtech

- DRAFT

POWER MANAGEMENT

Using the ±4ppm, 32.768kHz clock from the LF oscillator, the Real-Time Clock module keeps time with a maximum

error as low as two minutes per year. This compares favorably with a conventional error of two minutes per month for

the typical RTC chip.

The hardware of the Real-Time Clock is capable of 179-years of calendar operations (see Figure 6). All counting-chain

values are loaded at the same time into corresponding registers when the Fractions register is read. All values from

registers are loaded into the counting-chain when the Fractions register is written. The RTC continues normal opera-

Real-Time Clock

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Figure 6. Real Time Clock and Periodic Interrupt / Wakeup timer

16-bit Counter

Days (BIN)

0 - 65535

256 Hz

32-bit Time Interval

32-bit Counter

32-bit Comparator

32-bit Latch

Interrupt

Logic

Serial I/O

256

60

60

24

1 Hz

LSB

MSB

Minutes

(BCD)

0 - 59

Seconds

(BCD)

0 - 59

Fractions

(BIN)

0 - 255

Hours

(BCD)

0 - 23

32-bit Latch

LSB

Current Timer

Value

LSB

MSB

32.768 kHz

128