SIM800 Series_Multiplexer_Application Note_V1.04
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reply with a DM frame with the F-bit set to 1. Please refer to 3.1 for more details.
3.4 Closing Down DLC
The release of a DLC will be initiated from by the transmission of a DISC frame with the P-bit set to 1.
Confirmation of the DLC release is signaled by MS sending a UA frame with the F-bit set to 1. Once the
DLC has been released the MS enter disconnected mode for that particular DLC. If MS receiving the DISC
command is already in a disconnected mode it will send a DM response. Please refer to 3.6 for more
details.
3.5 Control Channel
Multiplexer control channel is the basic channel which is used to establish DLC, launch power saving, wake
up from power saving and implement flow control mechanism.
Control channel is the first channel established at the initiation of the multiplexer between the TE and MS
and it has the DLCI value 0.
UIH message frame is transmitted through control channel. All UIH message frame conform to the following
format.
Type
Length
Value 1
Value 2
……
Value n
Each box in the table represents a field of minimum size one octet.
The first type field octet has the following format:
1
2
3
4
5
6
7
8
EA
C/R
T1
T2
T3
T4
T5
T6
The EA bit is an extension bit. It is set to 1 in the last octet of the sequence. In other octets EA is set to 0.
SIMCom multiplexer only supports one octet is transmitted. So EA is always set to 1.
The C/R bit indicates whether the message is a command or a response.
The T bits indicate the type coding. Each command has a unique pattern of bit sequence. This means that a
single-octet type field can encode 63 different message types. Only single octet message types are defined
in the present document. Please refer 2.5.1 to 2.5.6 for more details.
The length field octet has the following structure:
