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Modbus RTU- S7 1200-write char type of data in modbus slave

Created by: luciferC4 at: 5/30/2010 10:11 PM (8 Replies)

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5/30/2010 10:11 PM	Rate (0)
luciferC4 Bronze Member Joined: 1/25/2006 Last visit: 11/6/2024 Posts: 257 Rating: (60)	Hi All, as modbus master I used S7 1200 and for modbus slaves I used non Siemens products. I want to write one data in slaves which type is char(byte). Is it possible to do? With this parameter I change counter in slaves. Thanks.

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5/31/2010 8:18 AM	Rate (0)
UMENCHO Diamond Expert Joined: 3/21/2006 Last visit: 11/1/2024 Posts: 10229 Rating: (1181)	Hello, Seems char type variable is not possible to read write. Data block structures for the DATA_PTR parameter These data types are valid for word reads of Modbus addresses 30001 to 39999, 40001 to 49999, and 400001 to 465536 and also for word writes to Modbus addresses 40001 to 49999 and 400001 to 465536. - Standard array of WORD, UINT, or INT data types, as shown below. - Named WORD, UINT, or INT structure where each element has a unique name and 16 bit data type. - Named complex structure where each element has a unique name and a 16 or 32 bit data type. For bit reads and writes of Modbus addresses 00001 to 09999 and 10001 to 19999. - Standard array of Boolean data types. - Named Boolean structure of uniquely named Boolean variables. Best regards, Hristo Mihalev

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5/31/2010 10:11 AM	Rate (0)
luciferC4 Bronze Member Joined: 1/25/2006 Last visit: 11/6/2024 Posts: 257 Rating: (60)	Thanks for answer. I knew for that but I hoped that maybe exist some possibility for this problem. Thank you again.

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5/31/2010 11:22 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 11/14/2024 Posts: 3027 Rating: (1057)	Hello luciferC4 don't give up hope just yet and please clarify the following first: IsyourModbus Slave device a"Modbus RTU"or a "Modbus ASCII" one? If it is a Modbus RTU device, your 1200 can directly talk to it and just because you can't select "char" as a datatype does NOT mean that you can't "embedd" a character as a value in a Word that you sentto the appropiate (holding) register init (e.g. "0" as an ASCII characters is a decimal value of 48) If it is however a Modbus ASCII Slave device, your 1200can NOT directly talk to it (and your 'char" question would now refer to a difference inprotocol rather than values that are transmitted inside a a message). You can however get Modbus RTU to Modbus ASCII converters and use them(google it, there's plenty cheap ones around). I suggestyou check the manual of your Modbus Slave andfeed back the info here if you have further questions. I hope this helps
	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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5/31/2010 2:13 PM	Rate (0)
luciferC4 Bronze Member Joined: 1/25/2006 Last visit: 11/6/2024 Posts: 257 Rating: (60)	Modbus slave communicate via Modbus RTU. Only two character I will use: 0 and 1. Please, send me instruction for further steps. Thanks.

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6/1/2010 10:43 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 11/14/2024 Posts: 3027 Rating: (1057)	luciferC4 Only two character I will use: 0 and 1. Please, send me instruction for further steps. Hello luciferC4 Can you please do the following first as (sort of) previously requested (my crystal ball is currently broken): I suggestyou check the manual of your Modbus Slave andfeed back the info here ... (Ideally you either post the manual for it here or a link to it.). Other things to do/check for you in the meantime are: - WhatModbus Modbus registers do you need to write to in the Slave? - Have a good read of section 6.3.2 of the S7-1200 manual and also check out page 191 in it which list the Modbus Function codes associated register addresses that the 1200 supports. Ihope this helps
	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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6/1/2010 1:09 PM	Rate (0)
luciferC4 Bronze Member Joined: 1/25/2006 Last visit: 11/6/2024 Posts: 257 Rating: (60)	Hello Fritz, In the first,in attachment you can seemanual for Modbus slave device. Litigious locations are 71 and 72. Those locations is type char and value of characters are "0" and "1" (71 HT/ switch real energy 72 HT/NT switch reactive energy ). With those parameters I can change counters for energy measuring (High and low tariff). I tried to embedd value as you advice me. In data block, I used location with WORD data type. Value of this location is 16#3131 (31 Hex=1 ASCII). Is it correct step? As result,I got nothing. I can't write. Have you idea where, maybe, I make mistake? Thanks. Attachment UMG103 modbus adrese.pdf (305 Downloads)

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6/1/2010 3:42 PM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 11/14/2024 Posts: 3027 Rating: (1057)	Thanks for info luciferC4, things are starting to make sense. Unfortunately, Janitza's Modbus Address list manualisnot all that helpful and somewhat confusing and here's what I make of it: When they say that the data type is "CHAR" they mean "1 Byte long" (see page 2, this is odd to begin with as Modbus does not really do Bytes, but this may not matter as you will simply always write to adress "71" & "72" together). It means though that you do NOT need (should) write an ASCII value of 31hex into it to send a "1" but instead you put a simple integer value of 1 into it (or 0101hex for the Register Word). Next "issue' are the Modbus addresses which do NOT comply with the Modbus addressing scheme. I think they forgot to mention that all addresses are so called Holding addresses and do require to add 40000 to them (I'm speculating here, but its the only way I can make sense out of it). Anyway, here's what I suggest you do: 1.) Write an E-Mail to info@janitza.de and seek clarifcation on the above. Ask them too what Modbus Function codes they support 2.) Try the following in the meantime (set Mode to "1" and Data length to "1" for the MB_Master" block in your 1200): 2a.)Write a value 0101hex to Address 40071 and see if it works 2b.)Write a value 0101hex to Address 40070 and see if it works (Modbus has the n-1 addressing regime oddity and who knows how Janitza took this into account so you may as wel ltry Address 40072 too). I hope this helps, good luckand let us know about the outcome please
	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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11/3/2017 6:09 AM	Rate (0)
Jen_Moderator Diamond Member Joined: 6/19/2017 Last visit: 9/6/2024 Posts: 8175 Rating: (172)	New question published by AutoGen_6455290 is split to a separate thread with the subject How to send a series of code to a sensor that contains 16 # 55.16 # 81.16 # 81.16 # 5 c, # 16 # 03?. Best regards Jen_Moderator

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