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CP340- USS Problem

Created by: dzeezz at: 3/13/2007 9:27 AM (4 Replies)

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3/13/2007 9:27 AM	Rate (0)
dzeezz Bronze Member Joined: 10/23/2006 Last visit: 10/23/2024 Posts: 48 Rating: (1)	Hello, Ihave Cpu314 with CP340. I use it to communicate with 10 Micromaster 420 Inverters thru USS protocol(The RS485 Bus is Terminated well on both end). I'vesend and recive from inverterscyclicaly one after another Inverter. My CP 340 settings is: - ASCII, 9600,8 bit,1 stop bit,Parity Even (the same as in all inverters). - On recipt of fixed number of characters (Message frame length=14) -Data flow Control= None -I use "Prevent overwriting" withBuffered Recive Message Frames=1 -Half duplex RS485 with Initial State of the Recive Line: R(a) 0V R(b) 5V In my program I cyclically send mesage to right inverter and waiting for its response.If I get response I send mesage and wait for response from next inverter,an so on... When time of waiting for response from inverter is elapsed(now its 300ms) I set error mesage and send mesage to next inverter. Adress of inverters are 1 to 10. My problem is: Sometime I have got error message from 2 inverters,always the same with adres number 3 and 10. Can you advise me what can I do to correct my problem?

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3/14/2007 8:34 AM	Rate (1)
Helmut_13 Posts: 2930 Rating: (432)	Hi dzeezz, I do not know how the USS is realised for the CP340 in a S7-300 System. I only know the S7-200 USS but the timing should be the same. In the S7-200 manual for a baud rate of 9600 each drive needs 50ms. Your 10 drives will need max. 500ms if no parameter are used. I know in the S7-200 you have to use an INIT with the numbers of drives you want to control. If ony one is connected but 31 are initialiysed then the token will need 50ms * 31 drives even if only one is connected. So check how many drives you have enabled and change from 300ms to 500ms. My experiances with USS: Cable: I always use standard Profibus cables with standard profibus connectors. NO selfe made cables because in the past I used it one time and I got lots of problems. Network: In the past I had USS-Network with two drives at the end and well terminated and the PLC in the network. Connectors and cables Profbus standard. One drive I was not able to control. After lots of tests and investigation I have changed the network so the drive with the problems I changed into the network (not at the end and so not terminated) and the PLC at one end and terminated. Since this modification it works. I do not know why but I think the problem was reflexions in th eUSS-Bus.. Filter: I always use the avaliable filter for each drive. I hope this helps. Helmut
Helmut_13 Posts: 2930 Rating: (432)
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3/14/2007 12:37 PM	Rate (0)
dzeezz Bronze Member Joined: 10/23/2006 Last visit: 10/23/2024 Posts: 48 Rating: (1)	Thank you very much for your response. I think that information about making electrical connection are very usefull for me. Yesterday Ireplace electrical connection and USS adresses of twoinverters(first with no communication problem,second have communication problem). Due to this I think that there are electrical problems. On the fronf panel of CP340(RS485 partner) there are Send and Recive LED. They switch ON and OFF durind reciving and sending. Almost all time they light cyclicaly, but sometimes there are some irregularities. It's look like sometimes there are no response from inverter. There are no possibilitie to use Profibus connectors with CP340 and Micromaster. In normal situation Isend data to inverter every75ms. Taht mean that I have 750ms cycle for reading 10 inverters. This 300ms is the time wich PLC waiting for response from inverter,thats mean when I send message to inverter and I don't getresponsefrom inverter in 300ms I set "Errormessage" and start sending message to next inverter. In my instalation every inverter have filter. Could you once again descript Network paragraph, becouse I can't undersand your descrition.Sorry. bye.

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3/17/2007 4:57 PM	Rate (1)
dzeezz Bronze Member Joined: 10/23/2006 Last visit: 10/23/2024 Posts: 48 Rating: (1)	I found why I can't comunicate with one from ten inverters . The problem was: Inverter with witch I had communication problem has Aderss numeber decimal:10. I send this adres 10 from S7-300, but in S7-300 program I had hexadecimal format of adres. So when I change adres in to A everything works well. Thanks for your attention. Bye

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7/30/2013 9:03 AM	Rate (0)
O_Moderator Diamond Member Joined: 4/24/2009 Last visit: 8/20/2024 Posts: 2682 Rating: (135)	New question was splitted to S7-314 and CP340 connected with 12 master drives CU2 with serial RS485 interface Best regards O_Moderator
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