Multiplexer User's Guide
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3.2.2 Escape sequence
When the multiplexer protocol is active only coded data is transmitted over the UART. The coding includes a header and a checksum. Therefore, the direct parsing of this sequence is not possible. An escape might be undetected because the decoded time relations may be disturbed.
The following transmission path for the ESC signal has been implemented:
•DTR is transported within the logical channel. To terminate a call, the normal way of using DTR is available. Please keep in mind that the multiplexer cannot transport this signal in real time. Please use a certain gap time between signaling with DTR.
•It is possible to detect “+++” on the customer multiplex application and transport this information via the MSC signal to the module (see Chapter 4.3.9).
•As an alternative, ATH may be sent on one of the other channels, for more detailed information please refer to [2].
3.3 Power saving
SLEEP mode reduces the functionality of the module to a minimum and, thus, minimizes the current consumption to the lowest level. SLEEP mode can be set with the AT+CFUN command which provides the choice of the functionality levels <fun>=0, 1, 5, 6, 7 or 8. For further details on power saving see [1] and [2].
If the module is in multiplexer mode, it is not recommended to activate SLEEP mode with AT+CFUN=<n>. For products supporting Multiplexer Protocol version 3, the best approach to properly control SLEEP mode in this case is to issue the PSC messages described in Chapter 4.3.10.
3.4 Bandwidth of logical channels
Please take into account that a data transmission, e.g. on channel 1, causes a transmission delay on the remaining channels (see chapter 3.1). The multiplexer mode according to the GSM 07.10 multiplexer protocol encapsulates data and AT commands into packets which may vary in length. Therefore a header including protocol information located at the beginning of the protocol data unit has to be transmitted. To summarize, if the module is set to 115200 bps and an incoming GPRS call requires 5 kByte per second, the two other channels have to operate within the range of the remaining 5 kByte per second.
If three large data transmissions are running simultaneously, the available bandwidth will be shared equally among all channels. In such a case if channel 2 and 3 were used for data transmissions, e.g. editing the phonebook, both channels would need to share a bandwidth of approximately 3 kByte per second.
Mux_guide_v06 | Page 16 of 36 | 30.06.2004 |