Modes Of Operation; Hardware Failure Reporting; Network Available Output - Iridium 9601 Product Developer Manual

Iridium Satellite LLC
9601 SBD Transceiver Product Developers Guide
V1.24 120505

3.3.3 Modes of Operation

The serial interface is always in one of three modes: command mode, SBD data mode or SBD session
mode. When the data port is in command mode, AT commands can be entered to control the 9601. In
command mode, flow control has no effect, with the RTS input ignored and the CTS output driven ON
(low). When in SBD data mode, the 9601 is transferring binary or text SBD message data to or from the
DTE.
In SBD data mode:
 All characters from the DTE not forming part of the message data are ignored (i.e. no AT
commands may be entered)
 No unsolicited result codes are issued.
 RTS/CTS flow control, if enabled, is active. When RTS is OFF (high), the 9601 suspends transfer
of data to the DTE; when CTS is OFF (high), the 9601 expects the DTE to suspend transfer of data to
the 9601.
When in SBD session mode, the 9601 is attempting to conduct an SBD session with the network. In SBD
session mode:
 The DTE must wait for the +SBDI session result code.
 All characters from the DTE are ignored.
 Unsolicited result codes are issued where those codes have been enabled.
Transitions between the modes of operation are performed automatically by the 9601 in response to the
SBD AT Commands; the DTE has no other control over the mode.

3.4 Hardware Failure Reporting

If the 9601 detects a hardware problem during initialisation, the 9601 may be unable to function correctly.
The 9601 notifies the DTE of this situation by issuing an unsolicited result code at the end of initialisation:
HARDWARE FAILURE: <subsys>,<error>
where <subsys> identifies the software subsystem that detected the error, and <error> is the
subsystem-specific error code.
Any AT commands that cannot be handled in the failure condition will terminate with result code 4
( " ERROR" ) .

3.5 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 application
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 9601 can successfully receive the Ring Channel, or, put more
simply, it can see a 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 9601 attempts to conserve power by increasing the ring search interval while
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