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Reading of DP Slaves using CPU317 and 4 nos of CP342-5 - Data getting overwritten

Created by: Sudheer Murthy at: 10/18/2006 2:08 PM (5 Replies)

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10/18/2006 2:08 PM	Rate (0)
Sudheer Murthy Posts: 6 Rating: (0)	We are having 4 different Profibus DP links using CP342-5 on CPU317. We are using DP-Recv and DP-Send blocks for reading and writing to the DP devices. Each DP master has its own set of Hardware addresses. For eg we have assigned 500 bytes for each DP master. If we are using 1 single DB for reading from multiple DP-Recv calls then we have a problem of data getting overwritten. For eg.One DP-Recv call for one master is overwriting the complete DB. Can you suggest the most optimum method of reading data from such a system. Thanks
Sudheer Murthy Posts: 6 Rating: (0)
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10/20/2006 2:38 PM	Rate (0)
J_Bell Posts: 5822 Rating: (412)	Dear Vortex, firstly of all I have a little Problem if you use 4 CP 342-5, because even for the last CPU 317-2AJ10 only 2 internal and 2 CP DP Master are allowed... secondly I wonder myself, if you use 4 CP 342-5 how did you program the FC1 and FC2 for each CP? What I talk about is the Configuration set for each Block. If you like you can post this one. Best regards J_Bell
J_Bell Posts: 5822 Rating: (412)
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10/23/2006 8:12 AM	Rate (0)
Sudheer Murthy Posts: 6 Rating: (0)	Mr.Bell, The new series of CPU317 support 4 DP masters. The catalog confirms the same. For use of FC1 (DP_RECV) and FC2 (DP_SEND) , we are using 2 DB's , one for receive data and second for send data. For eg. DB1 for FC1 and DB2 for FC2. The input image is received into DB1 and the output image is written from DB2. This is okay if there is one CP card as DP master. For reading from multiple masters, we have tried different options 1. Using multiple DB's for multiple masters, The problem withthis is that the multiple DB's eat up a lot of memory. 2. Using single DB for multiple masters. The problem with this is that everytime the data is read from a new master, the complete DB is overwritten. Even if we use this single DB as a scratch area, the data in the transferred area is also overwritten. I wanted to know of an efficient method for reading of all the slaves. I hope iam clearly describing my problem area. Thanks
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10/23/2006 8:59 AM	Rate (0)
Wizard Diamond Member Joined: 4/24/2006 Last visit: 11/15/2024 Posts: 8768 Rating: (1171)	Hello Vortex, Please let us know what parameters you use, when you call the FC1 and FC2. Especially the Send and Receive area. Best regards, Wizard

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10/23/2006 11:43 AM

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Sudheer Murthy

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HI,

I have attached a snapshot of the DP_RECV block. I have also put down the sequence in which we are executing the blocks. We are not having any delay between DP_RECV calls.
Here we find that data in DB1 and DB3 is also getting overwritten.
The Hardware addresses are in ascending order. DP Master 1 from 500 to 1000, DP Master 2 from 1000 to 1500 and so on.

1	DP_RECV - Master1 Move data into DB1
2	Transfer the data from DB1 to DB3
3	DP_RECV - Master2 Move data into DB1
4	Transfer the data from DB1 to DB3
5	DP_RECV - Master3 Move data into DB1
6	Transfer the data from DB1 to DB3

Attachment

DP Recv.JPG (947 Downloads)

10/23/2006 12:04 PM	Rate (0)
Wizard Diamond Member Joined: 4/24/2006 Last visit: 11/15/2024 Posts: 8768 Rating: (1171)	Hello, Did you have a look at following faq: http://support.automation.siemens.com/WW/view/en/18208090 Look also at point 5! You' re talking about DB1 as receive area, but in screenshot there is DB21? The data is put in DB21 from DBX0.0 and there are more than 800 bytes. Have you tried to put te other Receive data in DB21 from DBX900.0 and so on? Best regards, Wizard

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Created by: Sudheer Murthy at: 10/18/2006 2:08 PM (5 Replies)

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