Real Time Clock - Wavecom GR64 GSM/GPRS Integrator's Manual

Figure 28: Recommended circuitry for a TX_ON implementation

5.21 Real Time Clock

The real-time clock (RTC) is driven by a 32.768 kHz clock from an internal crystal
oscillator. The clock is divided by 32,768 to generate a clock with a 1 second period
that increments a 29-bit seconds counter. In addition, it can generate interrupts at a
programmed time. The following are the features of RTC:
•
•
•
An RTC alarm can be set by loading an appropriate value into the seconds alarm
register and enabling an interrupt via an AT-command.
The RTC relies on an uninterrupted 1.5 V (nominal) power supply (VRTC), whether the
Wireless CPU is powered off or on. The RTC-alarm operates from the VRTC supply,
and therefore utilizes a 1.5 V logic level. Users have the responsibility to provide a
backup battery to provide uninterrupted VRTC function when the Wireless CPU is
powered down.
Parameter
RTC accuracy
RTC accuracy
VRTC
GR64 Integrators Manual
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17-year time interval with 1 second resolution.
Programmed time alarm interrupt
Alarm output pin
Condition
Ambient (+25±2°C) operation
Extreme temperatures
RTC Operational supply voltage
range
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Min Typ Max
52.6 Secs/month
65.2 Secs/month
1.10 1.50 1.65
Unit
V