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
