3
Introduction
The 27.010 multiplexer protocol operates between an MS (e.g. GR/GS64) and a TE
(i.e. a host application) and allows a number of simultaneous virtual channels over a
serial asynchronous interface (e.g., a RS232 link). GPRS data, SMS data, AT
commands, unsolicited responses, etc. can be sent on different channels. When
virtual channels are established, they begin in AT command mode and each channel
acts like a virtual serial link from a host application point of view. For technical details
of 27.010 features please refer to [1]. GSM specs can be found at URL:
http://www.3gpp.org.
Physical Layer -
serial link
Multiplexer Layer
Convergence
Layers
MS Processes
Physical Layer -
serial link
Multiplexer Layer
Convergence
Layers
TE Processes
TE
MS
Figure 1: 27.010 protocol stack
Figure 1 shows the arrangement of the 27.010 protocol stack. The multiplexer layer
provides multiplexing of data; if the structure of the data has to be conveyed, a
convergence layer may be necessary.
The 3GPP 27.010 specification is intended to define a protocol that can be used to
emulate a serial port. Each virtual channel does best-effort emulation of a serial link.
Each channel may have individual flow control procedures for buffer management
purposes and Modem Status Command(MSC)s are used to emulate serial link control
signals (such as RTS, CTS, DTR, DSR, DCD).
AT+CMUX command enables the 27.010 MUX control channel and it is the first step
in starting the MUX. The basic MUX set up procedures are described in Appendix 1.
A MUX driver is needed on the host application side to enable the host application to
communicate with GR/GS64 using MUX protocol.
Gx64 APPLICATION NOTE
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27.010 MUX Feature
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