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TC3x Multiplexer User's Guide
TC3x_UG_01_V03.10 -
Released
Page 31/50
10.01.2002
Address
1 Octet
Control
1 Octet
Flag
1 Octet
0xF9
DLCI
DLCI: Data Link Connection Identifier
C/R:
Command / Response
EA:
extension bit; EA = 1
Frame type:
SABM Set Asynchronous Balanced Mode
UA
Unnumbered Acknowledgement
DM
Disconnected Mode
DISC
Disconnect
UIH
Unnumbered Information with Header check
UI
Unnumbered Information
P/F-Bit Poll- /Final - Bit
Length
1 or 2 Octets
Information
n Octets
FCS
1 Octet
Flag
1 Octet
0xF9
Checksum for address,
control and length
fields, also for the
information field in the
case of UI frames FCS.
Length
EA
Length: Length Information
EA:
extension bit;
EA = 1 -> 1 octet length information
EA = 0 -> >2 octets length information
EA
C/R
8 Structure of the multiplexer protocol
8.1 Introduction of the multiplexer protocol
The multiplexer protocol conforms with the multiplexer protocol GSM 07.10. The non-error recovery
mode was implemented with the basic option.
The frames have a start and a stop byte. A checksum is calculated to protect the transferred data.
Frame repetition is not enabled.
Data calls are transferred in the logical channel DLCI = 1 (DLCI: Data Link Connection Identifier). The
remaining DLCIs are in AT command mode.
The multiplexer protocol must be started and the logical channels opened in compliance with specified
procedures.
The chapter also gives you suggestions for the following aspects:
Opening logical channels without parameter negotiation
Opening logical channels with parameter negotiation
Closing of logical channels
8.2 Data link layer
The following
subchapters show the
detailed structure of a data
link frame.
Figure 15: Data link layer