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LZT 123 1836 69
5.19 Burst Transmission (TX_ON)
Pin Name Direction Function
39 TX_ON Output Transmit indication
Burst transmission is the period during which the GSM transceiver is transmitting RF
signals. TX_ON is an indicator that the module is transmitting.
A typical application may use TX_ON to blank adjacent receiver circuitry as a means
of protecting sensitive input stages.
5.20 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:
• 17-year time interval with 1 second resolution.
• Programmed time alarm interrupt
• Alarm output pin
An RTC alarm can be set by using the AT-command AT+CALA.
The RTC relies on an uninterrupted 1.5 V (nominal) power supply (VRTC), whether the
module is powered off or on. The RTC alarm operates from the VRTC supply, and
therefore utilize 1.5 V logic. Users have the responsibility to provide a backup
battery to provide uninterrupted VRTC function when the module is powered down.
RTC Accuracy
Parameter
Condition Max Unit
RTC accuracy Ambient (+25±2°C) operation
52.6
Secs/month
RTC accuracy Extreme temperatures
65.2
Secs/month