AT+CMUX Enter multiplex mode

All information provided in this section applies to the ASC0 interface only. The second interface ASC1 has no support of Multiplex mode.

Multiplex mode according to the ETSI TS 101 669 and GSM 07.10 enables one physical serial asynchronous interface to be partitioned into three virtual channels. This allows you to take advantage of up to 3 simultaneous sessions running on the serial interface. For example, you can send or receive data or make a call on the first channel, while the other two channels are free to control the module with AT commands.

The TC65 module incorporates an internal multiplexer and thus integrates all the functions needed to implement full-featured multiplex solutions. For the application on top, customers have the flexibility to create their own mul-tiplex programs conforming to the mulmul-tiplexer protocol. To help system integrators save the time and expense of designing multiplexer applications, SIEMENS AG offers WinMUX2k, a ready-to-use multiplex driver for Windows 2000 and Windows XP. Another approach is to develop customized solutions based on the sources of the WinMux2k driver.

Refer to [7] which provides a detailed description of the multiplex architecture and step-by-step instructions of how to install and configure the multiplex mode. The WinMUX2k driver and its source files can be supplied on request. Please contact your local distributor to obtain the latest installation software and user's guide.

Syntax

Parameter Description

Multiplexer transparency mechanism

0 Basic option

Subparameters defined in GSM07.07 are adjusted for control and logical channels as follows

0 UIH frames used only (control channel)

Test Command

AT+CMUX=?

Response(s)

+CMUX: (list of supported<mode>s) OK

Reference(s) PIN ASC0 ASC1 USB MUX1 MUX2 MUX3 Charge 4 ^Last

GSM 07.07, GSM 07.10 ! % ! % ! ! ! ! % %

<mode>^(num)

<subset>^(num)

Notes

• The write command is used to enter the multiplex mode. The setup of the logical channels is initiated by the TE, i.e. the TE acts as initiator. This means that the TE shall ensure that logical channels are established before any further actions on the channels can be started.

• There is a timeout of five seconds, if the multiplexer protocol is enabled and no multiplexer control channel is established. The GSM engine returns to AT command mode.

• The parameter maximum frame size (N1) of AT+CMUX in GSM 07.10 is fixed to 98 bytes and cannot be changed. All other parameters are not available.

• The Multiplex feature is not relevant for Java applications. The mode cannot be started if the ME is Java con-trolled.

If Java autostart is enabled with AT^SCFG, it is not possible to activate Multiplex mode on ASC0 or USB.

• Multiplexer mode requires character framing to be set to 8 bits, no parity and 1 stop bit. The setting can be made using (AT+ICF=3).

4.10.1 Restrictions on Multiplex mode

When the serial interface ASC0 is in multiplex mode, data and fax calls can only be set up on logical channel 1.

Due to this restriction, AT commands have a different behavior on channels 2+3 compared to channel 1. Several commands are not available, others return different responses. This section summarizes the concerned com-mands. For general rules and restrictions to be considered in Multiplex mode please refer to [7].

Table 4.1: Availability of AT Commands on Virtual Channels

1) Siemens GSM engines support the registers S0 - S29. You can change S0,S3,S4,S5,S6,S7,S8,S10 and S18 using the related ATSn commands (see starting from ATS0). The other registers are read-only and for internal use only!

2) The applicability of the +++ escape sequence depends on the customer's external application based on the Mulitplexer Protocol. Recommendations for implementing an appropriate modem status command (MSC) are provided in [7], Section

"Escape Sequence".

3) PDP contexts can be defined on any channel, but are visible and usable only on the channel on which they are defined (thus it is not possible to define a context on channel 2 and activate it on channel 3). GPRS connections can be

estab-Command Behavior on channel 1 Behavior on channel 2+3

+++ not usable, but see note ²⁾ not usable, but see note ²⁾

AT+CBST as described not usable

AT+CRLP as described not usable

AT+CG... (GPRS commands) as described see note ³⁾

AT+F... (Fax commands) as described not usable

AT&S as described not usable

ATA as described no Data Calls

ATD as described no Data Calls

ATDI as described not usable

ATL as described not usable

ATM as described not usable

ATO as described not usable

ATS6 ¹⁾ as described not usable

ATS7 ¹⁾ as described not usable

ATS8 ¹⁾ as described not usable

ATS10 ¹⁾ as described not usable

ATS18 ¹⁾ as described not usable

4.10 AT+CMUX

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lished on two channels at a time.

Table 4.2: Summary of AT commands with Different Behavior in Multiplex Mode

Command Description

AT\Q It is recommended to use hardware flow control (AT\Q3). XON/XOFF flow control (AT\Q1) is not supported in Multiplex mode.

See note regarding AT\Qn settings stored with AT&W if Multiplex mode is active.

AT&V Different default configurations on channels 1, 2 and 3.

AT&W Different user profiles can be stored on each channel.

AT+IPR Before you start Multiplex mode, it is recommended to set the ME to 57600 bps (minimum should be 4800 bps). For GPRS we suggest to use 115200 bps or 230400 bps.

In Multiplex mode, the write command AT+IPR=<rate> will not change the bit rate currently used, but the new bit rate will be stored and becomes active, when the module is restarted.

AT+IPR=0 Multiplex mode cannot be activated while autobauding is enabled.

AT+CALA On each channel an individual <text> message can be stored. but only one time setting applies to all channels. This means an alarm <time> set on one of the channels overwrites the time setting on all remaining channels. Therefore, the total number of alarm events returned by the read command AT+CALA? will always be

<n>=0, no matter whether individual text messages are stored.

When the alarm is timed out and executed the ME sends the URC only on the channel where the most recent alarm setting was made. The alarm time will be reset to "00/01/01,00:00:00" on all channels.

AT+CMEE Presentation mode can be separately configured for each channel.

AT+CNMA If Multiplex mode is activated the +CNMI parameter will be set to zero on all chan-nels, if one channel fails to acknowledge an incoming message within the required time.

AT+CNMI Phase 2+ parameters can only be used on one channel. The parameter for <mt>

and <ds> on the other channels have to be set to zero. If either a SM or a Status Report is not acknowledged, all +CNMI parameter will be set to zero on all chan-nels.

AT+CFUN If the ME is in Multiplexer mode, it is not recommended to activate SLEEP mode with AT+CFUN=<fun>. The best approach to properly control SLEEP mode in this case is to issue the PSC messages described in [7], Section "Power saving control (PSC)".

AT+CPMS Parameter <mem3> will be the same on all instances, but the settings of <mem1>

and <mem2> may vary on each instance.

AT^SSDA If one instance is set to <da>=1 and <mt>=1, then all other instances must be con-figured for <mt>=0.

4.10.2 Second serial interface ASC1

The second serial interface ASC1 is intended as an auxiliary interface for applications which need multiple par-allel access to the module (e.g. to query status information during a data call), but cannot use the GSM 07.10 multiplexing protocol. Therefore this interface offers limited functionality only.

• No DTR, DSR, DCD, RING signals. These hardware lines do not exist. As a result, AT commands controlling the behavior of these lines (AT&D, AT&C, AT&S) are not allowed and return ERROR.

• No presentation of ^SYSSTART URCs on ASC1. After restart or reset of the ME, either check that the URC has been sent on ASC0 or wait approximately 3 seconds before entering the first AT command on ASC1.

• No Autobauding. The hardware is not capable of automatically detecting the baudrate on this interface, so the AT command which selects autobauding (AT+IPR=0) is not allowed and returns ERROR.

• No CSD calls, so all related AT commands cannot be used and return ERROR.

• No fax calls, so all AT+F commands cannot be used and return ERROR.

• No GSM 07.10 Multiplexer. If issued on the second interface AT+CMUX=0 returns ERROR.

ASC1 is disabled when the multiplexer is enabled on the first serial interface ASC0. Yet, both ASC1 and the mul-tiplexer channel 2 are using the same parameters, and thus, the same user defined profile (if any). As a result, a user profile stored on multiplexer channel 2 takes effect on ASC1 after closing the multiplexer and starting up ASC1. Likewise, a user profile stored on ASC1 will be loaded on multiplexer channel 2.

This may be a problem when ASC1 is not connected, but flow control (for example AT\Q1 or AT\Q3) is stored to the user profile on the multiplexer channel 2. In this case, flow control takes effect on ASC1, when the multiplexer is switched off. If then for example a large amount of URCs is generated, their transmission might be stopped due to the flow control. To avoid this problem we recommend that you do not activate flow control on multiplexer channel 2 when you set up a user profile with AT&W.

4.11 AT^STPB

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