Technical data

SYSTEM CONNECTOR INTERFACE

LZT 123 8020 R1A

Hold time after falling edge of I

C CLK 0 ns

5.18 TX_ON - Burst Transmission

Pin Signal Dir Description

35 TX_ON O GSM radio device to transmit

Burst transmission is the time when a GSM transceiver unit is

transmitting RF signals. TX_ON indicates the radio device is

going into transmission mode.

5.19 Real Time Clock

Pin Signal Dir Description

25 VRTC - Voltage for the Real Time Clock

The Real Time Clock (RTC) provides the main microprocessor

with a time-of-day calendar and alarm, and a one-hundred-year

calendar. Its accuracy is shown in the table below

Parameter Min. Typ. Max. Units

RTC accuracy 25ûC 8 (21) 20 (52) ppm (s/month)

RTC accuracy extreme

temperatures

89 (231) 101

(262)

ppm (s/month)

The Real Time Clock operates in two modes when connected

to a separate power supply:

• RTC normal mode: the radio device is in ON or OFF mode

and it is supplied with power (VCC is applied).

• RTC back-up mode: VCC is disconnected and the RTC is

maintained by a separate backup power supply connected

to the VRTC input (see Figure 5.13 below).

Backup power is provided by a capacitor, golden-capacitor or

battery in your application and must be connected to the VRTC

pin. During RTC normal operation, the back up source will be

charged.

In back-up mode, the back-up source must provide enough

power for RTC operation. Refer to the table for the amount of

current required.

The following table shows voltage characteristics for both

modes.