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Modbus 6 digits size registers

Created by: kelertas at: 8/24/2010 12:53 PM (9 Replies)

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8/24/2010 12:53 PM	Rate (0)
kelertas Posts: 30 Rating: (0)	Hello, everybody. I want to ask You is this possible to read holding registers from modbus slave wich are 6 digits size? I use S7-226 PLC and MBUS_CTRL and MBUS_MSG soubroutines. In the manual of this soubroutine is wrote that registers are typicaly 5 digits size. So tell me how to read 6 digits size registers, please. best regards
kelertas Posts: 30 Rating: (0)
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8/24/2010 3:06 PM	Rate (0)
Robster Gold Member Joined: 5/28/2008 Last visit: 9/15/2025 Posts: 1344 Rating: (141)	Hi, where did you found the info, that you can read maximum 5 digits? Maybe I dont't understand right. Normally one register is one word, so 16 bits. If you want to read for example first holding register, you have to enter 40001 at the input "Addr" of MBUS_MSG. The value for the intput "count" is 1 in this case. But maybe you can explain little bit more detailed what you mean. regards

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8/24/2010 3:22 PM	Rate (0)
kelertas Posts: 30 Rating: (0)	ok I'll explain more detailed. I need to read not 5 digits value in register but the register wich address contained of six numbers. For example, I have a totalizer and the registers are addressed like this: 457829, 457833. So my question is is this possible to read such a modbus register with S7-226 PLC
kelertas Posts: 30 Rating: (0)
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8/24/2010 4:08 PM	Rate (0)
Robster Gold Member Joined: 5/28/2008 Last visit: 9/15/2025 Posts: 1344 Rating: (141)	Ok, I understood. It should be possible, because Inputparameter "Addr" has datatype DWORD. So 6 digit number can be entered there.

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8/24/2010 6:27 PM	Rate (0)
kelertas Posts: 30 Rating: (0)	big thanks for your comments. I'll try to do it
kelertas Posts: 30 Rating: (0)
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8/27/2010 7:57 AM	Rate (0)
kelertas Posts: 30 Rating: (0)	It does not work. when I i put address like 450917 to MBUS_MSG Adrr input, I get an error code "4". It means: "Error in request parameter. One or more of the input parameters (Slave, RW, Addr, or Count ) is set to an illegal value. Check the documentation for allowed values for the input parameters." Maybe someone knows the code for unlocking and modifiying the soubrutine. Or any others solutions how to solve this problem regards
kelertas Posts: 30 Rating: (0)
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8/27/2010 10:07 AM	Rate (0)
Mike J Platinum Member Joined: 10/9/2007 Last visit: 9/16/2025 Posts: 1283 Rating: (116)	Hi As far as I know, Modbus uses a Word for addressing information, not a DWORD. This means you could have maximum 65.536 addresses, and you are trying to read beyond that (457.829). Apart from that, take a look at this site http://www.simplymodbus.ca/FAQ.htm#Extabout Extended Register Addresses. Maybe you are using a modified version of Modbus(?) Mike J
	Energy Automation products: Sicam, Siprotec, Digsi
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8/27/2010 10:38 AM	Rate (0)
Robster Gold Member Joined: 5/28/2008 Last visit: 9/15/2025 Posts: 1344 Rating: (141)	Mh, strange. Have you got an older version of modbus library? I have version 1.2 and there is the address parameter of datatyp DWORD (see attached). Maybe internal is a conversion to WORD. But this makes no sense. I'm sorry to tell you, that you can't edit the modbus library block. Is it possible to get another register in the totalizer? Maybe you can make some settings there? I don't know this device... regards Attachment modbus.JPG (422 Downloads)

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8/27/2010 2:36 PM	Rate (0)
kelertas Posts: 30 Rating: (0)	The Input Addr is DWORD type. But I dont know how this function parse the Addr value. I mean, I supply the value for example 450102. That is "4" is function code and "50102" is the address of first register. The value 50102 is less then 65535, so theoreticaly everythink should be ok because for starting address 2 bytes are excluded. But nevertheless I get an error. P.S. Maybe somebody knows some another library for modbus master for S7-200
kelertas Posts: 30 Rating: (0)
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9/8/2010 11:59 AM	Rate (0)
adrian1982 Posts: 37 Rating: (3)	Ok, i hope this helps. In my app i have to read an power merter (PM810). Some of the data is stored as a real number (size:dword=2 holding registers for each data). So to read correctly 1 value i have to read 2 registers (eg. 411800+411801) and write them to VB846-VB849, and then i access the data as a floating point (dword - vd846) and so on... I have modbus library v1.2. Oh, for PM810 i have to activate those registry (witch are disabled by default) by a command in PM810. Maybe it's the same in your device. Attachment registry.JPG (467 Downloads)
adrian1982 Posts: 37 Rating: (3)
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