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1Si Modbus slave configuration (6ES7-138-4DF11-0AB0)

Created by: KappaTor at: 6/8/2009 9:37 PM (2 Replies)

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6/8/2009 9:37 PM	Rate (0)
KappaTor Member Joined: 2/22/2008 Last visit: 5/22/2023 Posts: 1 Rating: (0)	Hello .. I'm trying to set up communication with a Modbus master . My config are a C7 635 CPU and using 1M151-1 standard with the 1Si modbus slave (8b) In hardware manager i have configered it as RS232C with no flow control. Have connected only on terminal of 1si txd, rcd and pe with the master. Status led ok. I see tx and rx led flash every 3-4 second on the 1Si. I'm also not reciving any error codes in the program. Im using FB81 in OB1 as in exaple pdf from Siemens. With the same status bit memory and words. DB81 as instanse DB and DB100 as conversion table. I dont know the FC that the master is using. but its ment for it to read words from modbus address 0000. In DB100 , adresss 36, 38, 40 and 42 has the value hex 2A, and as I understand this means DB42, ie if the FC is 03,06 or 16, the master will "fetch" data from DB42.DBW0. In adress 4, DB100 i have but the value hex 8C, ie if the function code is 01, it will fecth data from MW200, Is this right? MW200 and counting uppwords are equal to DB42.DBW0. As the leds both rx and tx flashes regulary i recon there are communication on the modbus. This is point to point communication, and the 1Si is the only slave, with adress 1. Is theree any way for me to se the motbus frame that is sent on modbus and mayby what the respons also is? At this point i have still not be able to get any data to the master.

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6/8/2009 10:12 PM	Rate (0)
daga Gold Member Joined: 3/18/2009 Last visit: 12/6/2024 Posts: 306 Rating: (94)	I would suggest using a simulator to test your modbus settings. There are a few modbus simulators available that you can use. The one I have used in past is Modscan to simulate a modbus master on my laptop/PC. (I hope your laptop has an RS232 port!) You can download the demo version fromhere(It's enough for testing, though it may be a bit annoying to restart it again and again)

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6/13/2009 9:35 AM	Rate (0)
Paresh Posts: 116 Rating: (1)	HI, Please do not draw any conclusion from Tx and Rx led as there might be some exception communication going on between Modbud Master and slave. It will be easy to debug if you can tapp the communication between Modbus Master and Slave. Regards Paresh
Paresh Posts: 116 Rating: (1)
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