Specifications

SIM900 AT Command Manual
SIM900_AT Command Manual_V1.03 83 12/24/2010
OK
ERROR
Parameters
See Write Command
Response
If error is related to ME functionality:
+CME ERROR: <err>
Write Command
AT+CMUX=<mo
de>[,<subset>[,<
port_speed>[,<N
1>[,<T1>[,<N2>[,
<T2>[,<T3>[,<k>
]]]]]]]]
Parameters
<mode> multiplexer transparency mechanism
0 Basic option
<subset> the way in which the multiplexer control channel is set up
0 UIH frames used only
<port_speed> transmission rate
1 9 600 bits/t
2 19 200 bits/t
3 38 400 bits/t
4 57 600 bits/t
5 115 200bit/s
6 230 400 bits/t
7 460 800 bits/t
proprietary values, available if MUX NEW PORT
SPEED FTR is activated
8 921 600 bits/t
Proprietary values, available if MUX NEW PORT
SPEED FTR is activated
<N1> maximum frame size
1-32768 Default: 127
<T1> acknowledgement timer in units of ten milliseconds
1-255 Default:10 (100 ms)
<N2> maximum number of re-transmissions
0-100 Default:3
<T2> response timer for the multiplexer control channel in units of
ten milliseconds
2-255 Default:30
<T3> wake up response timers in seconds
1-255 Default:10
<k> window size, for Advanced operation with Error Recovery
options
1-7 Default:2
Reference
GSM 07.07 [13]
Note
The multiplexing transmission rate is according to the current serial baud
rate. It is recommended to enable multiplexing protocol under 115200