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Reference Guide
4.2.1.
Reset Sequence
To activate the Reset sequence, the Reset signal has to be set to LOW for a
minimum of 200µs. As soon as the reset is done, the application can send the
command AT8 and the AT interface will send an "OK" back to the application. If the
application manages hardware flow control, the AT command may be sent during the
initialization phase.
Figure 25.
Reset Sequence Diagram
Another solution is to use the AT+WIND command to get an unsolicited status from
the USR3500. Refer to the AT Commands Interface Guide at
http://www.usr.com/support/3500
4.3.
LED Status Indicator
The USR3500 has a red LED that indicates the current operational status of the
device.
Table 28.
USR3500 LED Status
USR3500 State
ON
OFF
for more information regarding AT commands.
LED Status
Permanently lighted
Flashing slowly
LED is ON for 200ms, OFF for 2s
Flashing rapidly
LED is ON for 200ms, OFF for
600ms
Very quick flash
LED is ON for 100ms, OFF for
200ms
OFF
Rev 1.0
Signals and Indicators
USR3500 Status
The modem is switched ON, but not
registered in the network.
The modem is switched ON and is
registered in a network (Idle mode).
The modem is switched ON and is
registered in a network (Connected mode).
The modem is switched on, and the
software downloaded is either corrupted or
non-compatible ("BAD SOFTWARE").
The modem is either switched OFF, or the
Flash LED has been disabled by the user*.
1/27/14
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