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Entry type: FAQ Entry ID: 73158403, Entry date: 05/15/2013

How do you read out the GSM/GPRS signal quality of the CP 1242-7 via the S7-1200 CPU?

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The S7-1200 CPU uses the Read Record function to read out the GSM/GPRS signal quality of the CP 1242-7 and store it in a DB.

CP 1242-7 firmware version V1.2 or higher

This FAQ response is not valid for CP 1242-7 V2.

To use this function you follow the procedure described in the table below:

No. Procedure
1 Create a DB with a structure tag as explained below: 

Fig. 01

2 Call RDREC cyclically in OB1 with the following parameters:

REQ = TRUE (to transfer the data record)
ID = Hardware identifier of the CP (go to Device Configuration and select the CP 1242-7 > Properties > Hardware Identifier)
INDEX = 12336 (data record number; 12336 for the GPRS signal quality)
MLEN = 12 bytes (maximum length of the data record data to be read)
RECORD = pointer to the data record in the DB created in step 1. 

Fig. 02

3 Click "Go online" and use the the "Monitor all" function to read the value of the "Signal quality" tag.

Fig. 03

Table 01

The values and their meanings for this tag are given in the table below:

Value Meaning Comments
0 GOOD -73… > -53 dBm
1 UNSTABLE -89… -75 dBm
2 WEAK -109… -91 dBm
3 NO_SIGNAL < -111 dBm
Table 02


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