Exchange of Signals to DP Slave over Profibus

8/29/2012 6:19 PM	Rate (0)
Vashist Posts: 7 Rating: (0)	Hello Experts In one of my project backupI have the following code written in one ofthe FC blocks //------------------------------------------------------------------------------- TAR1 #Inhalt_von_AR1 TAR2 #Inhalt_von_AR2 //------------------------------------------------------------------------------- L #ARRAY_StartByte_DB102 SLD 3 LAR1 L #S7_OUTPUT_DUR_IN SLD 3 LAR2 //------------------------------------------------------------------------------- OPN "S7 --> DUR A-B" L DBW [AR1,P#0.0] T PQW [AR2,P#0.0] // Input Wort0 des DUR // --------------------- L DBW [AR1,P#2.0] T PQW [AR2,P#2.0] // Input Wort 1 des DUR // --------------------- L DBW [AR1,P#4.0] CAW T PQW [AR2,P#4.0] // Input Wort 2 des DUR // --------------------- L DBW [AR1,P#6.0] CAW T PQW [AR2,P#6.0] // Input Wort 3 des DUR // --------------------- L DBW [AR1,P#8.0] CAW T PQW [AR2,P#8.0] // Input Wort 4 des DUR // --------------------- L DBW [AR1,P#10.0] CAW T PQW [AR2,P#10.0] // Input Wort 5 des DUR // --------------------- L DBW [AR1,P#12.0] CAW T PQW [AR2,P#12.0] // Input Wort 6 des DUR // --------------------- L DBW [AR1,P#14.0] CAW T PQW [AR2,P#14.0] // Input Wort 7 des DUR I understand that the above code is for taking the data from DB102 (S7 --> DUR A-B)fromthe stratting address "ARRAY_StartByte_DB102" and transferring it to the one of the DP Slave Station. The first twoWords of the DB102 from "ARRAY_StartByte_DB102"are Binary signal and the rest all the Analog Signals (Words). My question is that While transferring the Data packet to the DP slave for Bianry signal no CAW instruction is used, while it is used for all the analog signal. If anybody can throw some light on the reasonfor the above. Thank you all in advance. regards vashist

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Hello Experts

In one of my project backupI have the following code written in one ofthe FC blocks

//-------------------------------------------------------------------------------
TAR1 #Inhalt_von_AR1
TAR2 #Inhalt_von_AR2
//-------------------------------------------------------------------------------

L #ARRAY_StartByte_DB102
SLD 3
LAR1
L #S7_OUTPUT_DUR_IN
SLD 3
LAR2
//-------------------------------------------------------------------------------
OPN "S7 --> DUR A-B"
L DBW [AR1,P#0.0]
T PQW [AR2,P#0.0] // Input Wort0 des DUR
// ---------------------
L DBW [AR1,P#2.0]
T PQW [AR2,P#2.0] // Input Wort 1 des DUR
// ---------------------
L DBW [AR1,P#4.0]
CAW
T PQW [AR2,P#4.0] // Input Wort 2 des DUR
// ---------------------
L DBW [AR1,P#6.0]
CAW
T PQW [AR2,P#6.0] // Input Wort 3 des DUR
// ---------------------
L DBW [AR1,P#8.0]
CAW
T PQW [AR2,P#8.0] // Input Wort 4 des DUR
// ---------------------
L DBW [AR1,P#10.0]
CAW
T PQW [AR2,P#10.0] // Input Wort 5 des DUR
// ---------------------
L DBW [AR1,P#12.0]
CAW
T PQW [AR2,P#12.0] // Input Wort 6 des DUR
// ---------------------
L DBW [AR1,P#14.0]
CAW
T PQW [AR2,P#14.0] // Input Wort 7 des DUR

I understand that the above code is for taking the data from DB102 (S7 --> DUR A-B)fromthe stratting address "ARRAY_StartByte_DB102" and transferring it to the one of the DP Slave Station. The first twoWords of the DB102 from "ARRAY_StartByte_DB102"are Binary signal and the rest all the Analog Signals (Words). My question is that While transferring the Data packet to the DP slave for Bianry signal no CAW instruction is used, while it is used for all the analog signal.

If anybody can throw some light on the reasonfor the above.

Thank you all in advance.

regards
vashist

8/30/2012 7:17 PM	Rate (0)
captinjon Posts: 26 Rating: (0)	Hi Vashist, Its difficult to know why that would have being done without knowing what the slave is. Is it a drive? The CAW instruction simply swaps the byte order in the accumilator befor sending it to the slave. If you could tell us the slave type maybe that would help. Regards Jon

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8/30/2012 7:17 PM

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captinjon

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Hi Vashist,

Its difficult to know why that would have being done without knowing what the slave is. Is it a drive? The CAW instruction simply swaps the byte order in the accumilator befor sending it to the slave. If you could tell us the slave type maybe that would help.

Regards

Jon

8/31/2012 5:50 AM	Rate (0)
Vashist Posts: 7 Rating: (0)	Hello Jon Thanks for your reply !! The slave in question isDIGUREG (RG3-DUR)system from Siemens. The exchange of the signal is done with this DIGUREG system. The profibus siganl exchange listwith the DIGUREG system is attached herewith. Regards Vashist Attachment E:\PKV_Folder\Projects\01_Standard\02_Standard_RG3-DUR\Profibus Signals\ProfibusDIGUREG_e.pdf (159 Downloads)

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8/31/2012 5:50 AM

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Vashist

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Hello Jon

Thanks for your reply !!

The slave in question isDIGUREG (RG3-DUR)system from Siemens. The exchange of the signal is done with this DIGUREG system. The profibus siganl exchange listwith the DIGUREG system is
attached herewith.

Regards
Vashist

Attachment

E:\PKV_Folder\Projects\01_Standard\02_Standard_RG3-DUR\Profibus Signals\ProfibusDIGUREG_e.pdf (159 Downloads)

8/31/2012 6:55 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 6/9/2023 Posts: 2969 Rating: (1025)	Hello Vashist I am speculating here, but my guess is that the DIGUREG uses Little Endian format. If this is the case and sinceSiemensPLC's use BigEndian format, the high and low byte of each word (e.g.Integer value) need to be swapped, hence the CAW command. I hope this helps and you'll find more info about the Little vs Big endiandifferences at http://en.wikipedia.org/wiki/Endianness
Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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8/31/2012 6:55 AM

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fritz

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Hello Vashist

I am speculating here, but my guess is that the DIGUREG uses Little Endian format.
If this is the case and sinceSiemensPLC's use BigEndian format, the high and low byte of each word (e.g.Integer value) need to be swapped, hence the CAW command.

I hope this helps and you'll find more info about the Little vs Big endiandifferences at http://en.wikipedia.org/wiki/Endianness

Cheers

fritz

The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited.
To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.

8/31/2012 8:36 PM	Rate (0)
Vashist Posts: 7 Rating: (0)	Hello Fritz Thanks for your post !! I could get some idea about the "Little Endian" and "Big Endian" formats and I could understandthe idea of swapping the bytesfor the transferred words. WhatI couldn'tunderstand was that why the swapping is done only for the analog signals (words) and whyis it not done for the first two words which are the binary signals. Can you please throw some light on this ? Thanks and Regards Vashist

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8/31/2012 8:36 PM

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Vashist

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Hello Fritz

Thanks for your post !!

I could get some idea about the "Little Endian" and "Big Endian" formats and I could understandthe idea of swapping the bytesfor the transferred words.

WhatI couldn'tunderstand was that why the swapping is done only for the analog signals (words) and whyis it not done for the first two words which are the binary signals.

Can you please throw some light on this ?

Thanks and Regards
Vashist

8/31/2012 9:59 PM	Rate (0)
captinjon Posts: 26 Rating: (0)	I think its not required on the binary data because it was programmed in the right order from the start, the analog data carnt be programmed correctly because the value in the plc would incorect. Hope this makes sense Jon

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8/31/2012 9:59 PM

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captinjon

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I think its not required on the binary data because it was programmed in the right order from the start, the analog data carnt be programmed correctly because the value in the plc would incorect.

Hope this makes sense

Jon

9/3/2012 10:59 AM	Rate (0)
Vashist Posts: 7 Rating: (0)	Hello Captinjon Hello Fritz Thanks for your posts!! I think what you have posted is correct. The idea of DIGUREG using Little Endian format and SiemensPLC's using BigEndian format seems to be correct and because ofthe above thehigh and low byte of each word (e.g.Integer value)would have beenswapped,using theCAW command in the code. Also the idea as given by Captinjonfor thebinary data,that it might havebeen have been programmed in the right orderfor getting the binary data also seems to be correct. I again thankyouboth ofyou for the clarifications and the posts. I will alsotry toget the confirmation for the above from the concerned department for DIGUREG in Siemens. Regards Vashist

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9/3/2012 10:59 AM

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Vashist

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Hello Captinjon
Hello Fritz

Thanks for your posts!!

I think what you have posted is correct.

The idea of DIGUREG using Little Endian format and SiemensPLC's using BigEndian format seems to be correct and because ofthe above thehigh and low byte of each word (e.g.Integer value)would have beenswapped,using theCAW command in the code.

Also the idea as given by Captinjonfor thebinary data,that it might havebeen have been programmed in the right orderfor getting the binary data also seems to be correct.

I again thankyouboth ofyou for the clarifications and the posts.

I will alsotry toget the confirmation for the above from the concerned department for DIGUREG in Siemens.

Regards
Vashist

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