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4.16
MUX
4.16.1
Services
4.16.1.1
MUX Open Service
The following procedure describes how to open the MUX service:
1.
Send the AT+CMUX command to the g20 for initiation of the GSM 07.10 protocol.
2.
Wait for the OK response.
3.
Open the MUX within ten seconds (otherwise, the g20 will exit the MUX mode and revert back to one channel in
0705/0707 mode).
A maximum of three channels can be opened: One channel for control, and two channels for information.
• Use Channel 1 for CSD or GPRS.
• Use Channel 2 for the AT Command set.
A minimum of two channels must be opened: The control channel , and data channel.
4.16.1.2
MUX Close Service
The following procedure describes how to close the MUX service:
1.
Close all CSD/GPRS connections.
2.
Close all data channels (DLC1 & DLC2).
3.
Close MUX, or channel 0 (DLC0), or toggle the hardware DTR signal.
4.16.1.3
Data Transfer
After all the MUX channels are opened, the user can send and receive data over the two virtual channels; Channel 1 and
Channel 2. The user can also send and receive MUX command data on the control channel (DLC0), as in testing for an echo.
4.16.1.4
Two Channel Limitations
Using two channels has the following limitations:
• Channel 1 should be used for CSD/GPRS/FAX. AT command usage on this channel is allowed only for establishing or
releasing a connection.
• Channel 2 should be used for AT commands, voice call and SMS.
• The g20 profile setup, (S-register), is the same for all channels (one modem). For example, when the atsx command is sent
from either Channel 1 or Channel 2, the modem S-register changes and affects both channels.
98-08901C68-O
AT Commands Reference
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