Modem User Manual

LZT 123 1834 70

5.19 Burst Transmission (TX_ON)

Pin Name Direction Function

35 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. TX_ON is active HIGH.

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 loading an appropriate value into the seconds alarm

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