Specifications

XT55 Hardware Interface Description
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XT55_hd_v00.02 Page 64 of 116 17.03.2004
3.12.2 Outputs
3.12.2.1 Synchronization signal
The synchronization signal serves to indicate growing power consumption during the
transmit burst. The signal is generated by the GSM_SYNC pin. Please note that this pin can
adopt two different operating modes which you can select by using the AT^SSYNC
command (mode 0 and 1). For details refer to the following chapter and to [1].
To generate the synchronization signal the pin needs to be configured to mode 0 (= default).
This setting is recommended if you want your application to use the synchronization signal
for better power supply control. Your platform design must be such that the incoming signal
accommodates sufficient power supply to the XT55 module if required. This can be achieved
by lowering the current drawn from other components installed in your application.
The timing of the synchronization signal is shown below. High level of the GSM_SYNC pin
indicates increased power consumption during transmission.
Figure 23: GSM_SYNC signal during transmit burst
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The duration of the GSM_SYNC signal is always equal, no matter whether the traffic or
the access burst are active.
Transmit burst
1 Tx 577 µs every 4.616 ms
2 Tx 1154 µs every 4.616 ms
300 µs
GSM_SYNC signal
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