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5.18 TX_ON - Burst Transmission
5.19 Real Time Clock
LZT 123 7589 R1A
5. SYSTEM CONNECTOR INTERFACE
Parameter
2
Frequency I
C CLK
2
High or low I
C CLK
Delay time after falling edge of I
CLK
Hold time after falling edge of I
CLK
Pin
Signal
35
TX_ON
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.
Pin
Signal
25
VRTC
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.
RTC accuracy
25°C
RTC accuracy
extreme
temperatures
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.
Min.
1.2
100
2
C
0
2
C
Dir
Description
O
GSM radio device to transmit
Dir
Description
-
Voltage for the Real Time Clock
Typ.
8 (21)
89 (231)
Typ.
Max.
Units
400
kHz
µs
ns
ns
Max.
Units
20 (52)
ppm (s/month)
101 (262)
ppm (s/month)
49
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