Serial Data Interface; Network Available Output; Dc Supply Indicator Output - Iridium 9603 Developer's Manual

Iridium 9603 SBD Transceiver Product Developers Guide
Revision 3.1
3.3

Serial Data Interface

The data/fax serial interface is an RS-232 9-wire interface at 3.3V digital signal levels over which the 9603/9603N and FA transfer
commands, responses, and SBD message data. With respect to this interface, the 9603/9603N behaves as a DCE (Data
Communication Equipment), and the FA behaves as a DTE (Data Terminal Equipment).
If RS-232 voltage levels are needed, the FA must include an LVTTL/RS-232 level-shifter.
Autobaud is not supported. The baud rate can be set via the AT+IPR command. The default rate is 19200 bps.
See the ISU AT Command Reference Specification for information on the data/fax interface.
3.4

Network Available Output

This is a digital output that can be used by an application to know when the transceiver has visibility to the satellite network. This is
useful in applications where the transceiver may move around terrain that reduces the amount of time that clear line of sight to the
satellite constellation is available. The Product Developer can use this output to preserve battery life by reducing the number of
attempted transmissions by including this logic output in the application decision logic.
Network Available means only that the 9603/9603N can successfully receive the Ring Channel, or, put more simply, it can see an
Iridium satellite. Network Available is not a guarantee that a message can be successfully sent. The Network Available state is
evaluated every time the Ring Channel is received or missed. If the Ring Channel is visible, then that is typically every 4 seconds.
If the Ring Channel is not currently visible, then the update period can be as long as 2 minutes, depending on how long the lack of
satellite visibility existed. This is because the 9603/9603N attempts to conserve power by increasing the ring search interval while
the satellites are not visible. Every time a ring search fails, the time to wait is increased and eventually limits at 120 seconds.
If Network Available is currently off, the Field Application may still attempt an SBDI[X] session. This will force the 9603/9603N
Transceiver to look for the Ring Channel immediately, and on finding it, to attempt to send the message. In this case Network
Available will not come on immediately. The Network Available does not turn on while in a +SBDI session. It will however turn on 4
seconds later assuming that the Ring Channel is present. After the SBD session completes, the 9603/9603N performs a new Ring
Channel search sequence, at the end of which Network Available gets turned on. That can take between 4 and 12 seconds.
The wait time between search windows is reset to 4 seconds every time a search succeeds. Otherwise it continues to increase. So
if the +SBDI attempt fails to find the ring channel, the search window does not reset to 4 seconds.
Note that the behavior of +CIEV:1 is identical in to that of the Network Available output.
3.5

DC Supply Indicator Output

A DC supply indicator signal is provided by the 9603/9603N which could be used directly for driving an LED to provide a visible
indication that the Transceiver supply is on. Alternatively the output signal could be used in application logic to determine if the
internal Transceiver power supply is on.
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Distribution of guide restricted to product developers only • Information contained in this guide is subject to change without notice.
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