SH3003 Datasheet, PDF (18/30 Pages) Semtech Corporation – MicroBuddy® Support IC for Microcontrollers

SH3003
POWER MANAGEMENT
Application Information (continued)
Not authorized for release outside of Semtech - DRAFT
Real-Time Clock
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-
tions when VDD is absent, if backup power is available.
LSB
LOAD 32-bit Latch
MSB
Current Timer
Value
32.768 kHz
128 ^{256 Hz}
32-bit Counter
RESET
256 ^{1 Hz} 60
60
24 16-bit Counter
Fractions
(BIN)
LSB ^{0 - 255}
Seconds
(BCD)
0 - 59
Minutes
(BCD)
0 - 59
Hours
(BCD)
0 - 23
Days (BIN)
0 - 65535
32-bit Comparator
LOAD 32-bit Latch
LSB ^{32-bit Time Interval}
MSB
Interrupt
Logic
Serial I/O
IO/INT
14
Figure 6. Real Time Clock and Periodic Interrupt / Wakeup timer
©2006 Semtech Corp.
18
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