Flag Sequence; Address Field; Table 2: Address Field; Table 3: Assignment Of The Dlci - Siemens Mux_guide_v06 User Manual

Multiplexer User's Guide
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4.2.1 Flag sequence

A flag sequence is a specific bit pattern (usually 11111001; hexadecimal: 0xF9) used to mark
the beginning and the end of a frame of data.
Each frame begins and ends with a flag sequence. Only one flag sequence occurs between
any two frames. If two successive flag sequences do occur, the frame is regarded as being
empty and is discarded.
The flag sequence is used for the synchronization of frames.

4.2.2 Address field

Data link connection identifier is a frame relay term defining a 10-bit field of the address field.
The DLCI identifies the data link and its service parameters, including the frame size.
The values for the Data Link Connection Identifier (DLCI) are dynamically defined apart from
DLCI = 0.

Table 2: Address field

EA C/R
DLCI: Data Link Connection Identifier
C/R: Command / Response
EA: extension bit; EA = 1

Table 3: Assignment of the DLCI

Multiplexer control
(see chapter 4.3.6)
AT commands, data, fax, GPRS
AT commands, GPRS
The command/response bit identifies the frame as a command or response. A command
contains the address of the data link connection to which the command is sent. A response
contains the address of the data link connection sending the frame.

Table 4: Use of the command/response bit

Command/Response
Command
(SABM, DISC)
Response
(UA, DM)
Every command expects a response. No provision is made to repeat the command if no
response is received.
Mux_guide_v06
DLCI
DLCI number (decimal)
0
channel
1
2,3
Direction
Customer µC
GSM engine →
Customer µC → GSM engine
GSM engine
Page 18 of 36
Priority
0
highest priority
7
7
C/R
→ GSM engine 1
0
Customer µC
0
→ Customer µC 1
s
m
o b i l e
30.06.2004