Software Switching To Command Mode; Happy Flow; Escape-Sequence In Data - Javad HPT404BT Operator's Manual

3.1.1. Software Switching to Command Mode

On power-up the radio modem is in data-mode. To switch to command mode the special byte-sequences
with special 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 Command mode and
vice versa.

Happy Flow

1. In data-mode the unit starts looking for the Escape-sequence if there is no data from DTE (Data
Terminal Equipment) 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 command 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.)
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Command Line Interface
Command Line Interface Convention
Software Switching to Command Mode
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