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CP341 in PCS 7 as Modbus Master

Created by: JCrox at: 7/19/2007 10:10 AM (10 Replies)

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7/19/2007 10:10 AM	Rate (0)
JCrox Regular Member Joined: 4/29/2007 Last visit: 3/15/2021 Posts: 26 Rating: (1)	Hi all, I'm trying to use a SND_341 Block in CFC to send Modbus commands to a slave. I believe the block uses P_SND_RK (FB123). I have configured to do Modbus by setting R_Type to 'X' etc and have interconnected the S_DATA input of type ANY to a datablock of 6 bytes in length(DB1000). Note that interconnection only down todatablock level. I get the following error reported in STATUS: 16#1E0D This apparently means "Request aborted due to complete restart, restart or reset." I've tried setting and resetting the RESET parameter online whilst setting REQ from off to on... Any ideas would be very much appreciated. I believe I have the local address correct as it automatically filled the subnet, address and slot correctly. I might have not configured the PtP connection in netpro correctly. I've placed an other station object and connected it to a PtP subnet but cannot connect that subnet to the CP341 residing in the IM153 DPSlave. Do I need to do this? Many thanks. John

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7/20/2007 12:10 PM	Rate (0)
JCrox Regular Member Joined: 4/29/2007 Last visit: 3/15/2021 Posts: 26 Rating: (1)	I've had a little more luck... I can now get function codes out to my slave, the slave responds correctly (I ask for two registers and I get LEN = 4 on a NDR edge). However, the datablock does not seem to have the data from the slave. In my attached CFC you'll see that I have latched the NDR and writen to EN_R to prevent further reads. This is just to try and find out what's going on. But I still can't work it out . I repeatedly get an error in my send block (STATUS = 0830H) but this is not documented in the manuals so I'm not sure what it means. Any help would be greatly appreciated. I can see plenty of examples in Ladder using FB7 and FB8 but none in CFC using FB120 and FB121. Thanks John Attachment ModbusCFC.JPG (895 Downloads)

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7/20/2007 12:30 PM	Rate (0)
JCrox Regular Member Joined: 4/29/2007 Last visit: 3/15/2021 Posts: 26 Rating: (1)	Sorry for replying to my own post like this but I keep trying things. The MODB_SL parameter should be 0 as I'm a Master. This did not make it work however. I've just got a new error in the SEND STATUS (E32H). Again, this is not in the PtP manual. John

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7/21/2007 3:00 AM	Rate (0)
JCrox Regular Member Joined: 4/29/2007 Last visit: 3/15/2021 Posts: 26 Rating: (1)	OK... I found the reason for the 0830H error code I think. The reply monitoring time Hardware Configuration parameter was set too low. I had to look in the ASCII Modbus Master manual to find the error code but I assume this also applies to the RTU driver. Now, I just need to solve the Receive problem. John

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7/23/2007 1:46 AM	Rate (0)
JCrox Regular Member Joined: 4/29/2007 Last visit: 3/15/2021 Posts: 26 Rating: (1)	Is this requirement really unusual? Does any one have any experience with using a CP 341 in PCS 7 (CFC) as a Modbus Master? The blocks are there but they just don't seem to be working for me. Any assistance would be really appreciated. I really don't want to have to mashFB7 and FB8 into blocks able to be used in CFC myself whent the blocks already exist. I'm not sure whether any Siemens people are possibly able to help me out here butI believe I've used these blocks according to the online help and configured thehardware according to the Modbus Master PDF so I am at a real loss to know where to go from here, particularly as the status messages I'm getting do not appear to be listed in any of the manual (830, E32, 1E0D). Many Thanks...

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11/3/2008 9:40 PM	Rate (0)
MrGreg Member Joined: 10/31/2008 Last visit: 9/21/2023 Posts: 1 Rating: (0)	We has a similar problem with a PCS7 and Modbus integration. We could see a transmit/request from the CP module, but the CP module never saw the reply. Using a Modbus 'sniffer', we could see the field device was sending the proper reply. Wewere using a Siemens cable P/N 6ES79023AB000AA0 to 'breakout' the pins from the CP module to a terminal strip for easy wiring. Since this is really a RS422 cable,Siemens swaps pins 9 & 11 internally. Therefore, to wire to pin 11 of the CP module, we have to connect to pin 9 of this cable. Once we made this wiring change, we begin to see data received by the CP Module. Hope this helps...

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1/28/2013 2:44 PM	Rate (0)
Chandra Tiwari Posts: 247 Rating: (2)	Hello to all, M also facing the same issuee :(
Chandra Tiwari Posts: 247 Rating: (2)
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1/28/2013 4:35 PM	Rate (0)
Kaulquappe Posts: 3093 Rating: (323)	Hello Ravi, it is an error in your user program. As you didn't evaluate SFCERR, I can only give you some possibilities: - Send DBor Receive DB too short - Receive DB not available - P_SND_RK R_TYP=X is missing Regards, Kaulquappe
Kaulquappe Posts: 3093 Rating: (323)	Last edited by: Kaulquappe at: 1/28/2013 4:37 PM
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3/21/2013 11:57 AM	Rate (0)
Chandra Tiwari Posts: 247 Rating: (2)	Hi Kaulquappe, I am still facing the issue. Is there any ready made clock so that i can download and use it it in my project.
Chandra Tiwari Posts: 247 Rating: (2)
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7/2/2013 5:09 AM	Rate (0)
efraustro Posts: 4 Rating: (0)	Hi everyone, I solved this issue by not including directly the subroutine in OB1. I used to have the routine there: @OB1 CALL "MODBUS_COMM" .. . i had to move it to another function and inside that function include my subroutine. OB1 --> FCXX --> CALL MODBUS_COMM This happen because the stack pointer is reset while doing the transaction with the slaves and u lose sequence in the MODBUS BLOCKS (i forgot the name of them). Hope this help for u guys..
efraustro Posts: 4 Rating: (0)
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This contribution was helpful to 1 thankful Users Kaulquappe

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