Oct 18, 2011

Reading Messages of Modem Connected with PLC

In the latest applications modems are used with PLC for the remote control applications. Modems have find their way to be sued with PLC for better remote monitoring applications. We have already discussed as How to send Message through GSM Modem and also abot the SMS through SCADA & Modem. Today we will see the AT command used for sending the message received on GSM Modem to the Terminal Equipment(TE).

AT Command for Message Transfer to TE :-
The indication will be sent from the network to TE when TE is active; for example, DTR signal is ON. controls the processing of unsolicited result codes specified within this command, sets the result code indication routing for SMS-DELIVERs, for CBMs and for SMS-STATUS-REPORTs. defines the handling method for buffered result codes when 1, 2 or 3 is enabled. If ME does not support requested item (although TA does), final result code +CMS ERROR: is returned. Test command returns the settings supported by the TA as compound values.

NOTE: Command Select Message Service +CSMS should be used to detect ME
support of mobile terminated SMs and CBMs, and to define whether a message
which is routed directly to TE should be acknowledged or not.

SYNTAX :-
AT+CNMI= [,(mt) [,(bm) [,(ds) [,(bfr)]]]]

Now let us see the meaning of Mode , , , , and and values associated with them.

Mode Values:-
0 -- Buffer unsolicited result codes in the TA. If TA result code buffer is full,indications can be buffered in some other place or the oldest indications
may be discarded and replaced with the new receiver indications.
1 -- Discard indication and reject new received message unsolicited result
code when TA-TE link is reserved (e.g. in on-line data mode). Otherwise
forward them directly to the TE.
2 -- Buffer unsolicited result codes in the TA when TA-TE link is reserved
(e.g. in on-line data mode) and flush them to the TE after reservation.
Otherwise forward them directly to the TE.

(mt) Value :-
0 -- No SMS-DELIVER (message to ME) indications are routed to the TE.
Default.
1 -- SMS-DELIVER is stored in ME. Indication of the memory location is
routed to the TE by using the unsolicited result code.
2 -- class 0, class 1 and class 3 SMS-DELIVERs are routed directly to the TE
using unsolicited result code.
3 -- Class 3 SMS-DELIVERs are routed directly to TE using unsolicited result
codes defined in =2. Messages of other data coding schemes
result in indication as defined in =1.

(bm) Value :-
0 -- No CBM indications are routed to the TE.
2 -- CBM is routed directly to the TE by using the unsolicited result code:
+CBM: (PDU mode enabled)
or
+CBM: ,,,,
(text mode enabled)
refer to 03.41, Content of message is limited to 82 bytes and total pages
are no more than 15.

(ds) Values :-
0 -- No SMS-STATUS-REPORTs are routed to the TE
1 -- SMS-STATUS-REPORTs are routed to the TE using unsolicited result
code:


We hope that CNMI AT command is clear after understanding the above things. We will discuss more about GSM Modem Communication with PLC and the AT commands used, till then you can subscribe to get all latest updates by E Mail.
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