NAL RESEARCH CORPORATION A3LA-R, User Manual

Page: 29 / 159

A3LA-R-MIL-MOD User Guide Version B
Document Number: 451-93156-001A 29 of 159
7 M
ODES OF
O
PERATION
The A3LA-R serial data port 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 A3LA-R. In command mode, flow control has no effect, so the RTS input ignored
and the CTS output driven ON (low). When in SBD data mode, the A3LA-R 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 A3LA-R suspends
transfer of data to the DTE; when CTS is OFF (high), the A3LA-R expects the DTE to
suspend transfer of data.
When in SBD session mode, the A3LA-R attempts to conduct an SBD session with the network.
In SBD session mode:

The DTE must wait for the +SBDI [X][A] 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 A3LA-R in
response to the SBD AT commands; the DTE has no other control over the mode.