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Command Line Interface
Command Line Interface Convention
Software Switching to Maintenance Mode
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3.1.1. Software Switching to Maintenance Mode
Software Switching to Maintenance Mode can be utilized if Data/Maintenance Port (DP/MP)
control line is set to High Z (or 3.3v) level. To switch to Maintenance mode the special byte-
sequences withspecial meanings are used:
• Escape-Sequence: “+++” with 20 ms guard time before and after the command characters
• Escape-Acknowledge: “@00<CR><LF>” 20 ms toggling on CTS control line needed to
acknowledge switching from Data to Maintenance mode and vice versa. In Maintenance
mode, the unit’s serial port must keep CTS line always active.
Happy Flow
1. In data-mode the unit starts looking for the Escape-sequence if there is no data from DTE
for more than 20 ms (Start Guard Time).
2. If the unit detects the Escape-Sequence:
• The transmitter continues sending over the air the data received from DTE before Escape-
Sequence and buffers the data from DTE;
• The Receiver immediately stops forwarding to DTE the data received over the air and
buffers it instead.
3. The radio unit waits for 20 ms and then sends Escape-Acknowledge to DTE if there is no
data from DTE during 20 ms of Stop Guard Time.
4. The unit goes to Maintenance mode and discards Escape-Sequence from input buffer. The
modem is immediately ready to receive commands. At the same time it continues
buffering the data received over the air since step 2.
Escape-Sequence in Data
During its waiting in step 3, the unit receives data from DTE:
• The unit sends buffered Escape-Sequence from DTE to the air;
• The unit sends all buffered data received from the air since step 2 to DTE and stays in
data-mode (i.e. transmits data received from DTE over the air – including the just
received, unexpected, data and forwards data received over the air to DTE.)