www.beamcommunications.com
20
9602 SBD Modem | Installation and User Manual
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 9602 SBD MODEM. 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 9602 SBD MODEM 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 9602 SBD MODEM
suspends transfer of data to the DTE; when CTS is OFF (high), the 9602 SBD MODEM expects
the DTE to suspend transfer of data to the 9602 SBD MODEM.
When in SBD session mode, the 9602 SBD MODEM 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 9602 SBD MODEM
in response to the SBD AT Commands; the DTE has no other control over the mode.
Hardware Failure Reporting
If the 9602 SBD MODEM detects a hardware problem during initialization, the 9602 SBD MODEM
may be unable to function correctly. The 9602 SBD MODEM notifies the DTE of this situation by
issuing an unsolicited result code at the end of initialization:
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”).
