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access the 50000+ register with a S7-1200 as RTU modbus master

Created by: Connit at: 11/9/2016 3:42 PM (5 Replies)

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11/9/2016 3:42 PM	Rate (0)
Connit Posts: 5 Rating: (0)	Hi, Equipment : as master CPU 1214C DC/DC/DC (6ES7 214-1AG40-0XB0) with CM1241 (6ES7 241-1CH32-0XB0) as slave energy counter COUNTIS E43 My problem : I need to access register 50000+ on my slave but I found that the s7-1200 can't do it naturaly . I found the program using the mode 104 but my slave don't reconize this mode. Is there any other way to access the data I need ?
Connit Posts: 5 Rating: (0)
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11/10/2016 4:01 AM	Rate (0)
danw Gold Expert Joined: 3/28/2010 Last visit: 3/27/2025 Posts: 1133 Rating: (220)	All Modbus addresses/registers are 16 bit binary numbers starting at 0 and going up to 65535. A common convention is to use a leading numeral to indicate whether the value is a holding registor or an input register Function Code 03 (read input register(s)/addresses in memory area known as (4)xxxxx Function Code 04 (read holding register(s)/addresses in memory area known as (3)xxxxx Note that the leading numeral (3) or (4) is not part of the Modbus message, it is merely a convention to identify what type register/address it is. All that said, 50000 is within the range of 0 to 65535. If the master required a leading numeral (4), then the highest accessible register/address would be (4)65535. 30 years ago, both Masters and slaves were known to have limited address/register ranges. A modern Modbus master should be implemented to provide access to all 65536 address/registers. Whether the S7 does or not, I don't know. Nothing says it must have that many, just that there's a limit at 65536. Some masters require data entry of the leading (4) or (3), other masters do not. What happens when you try to access a slave register at (4)5xxxx?

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This contribution was helpful to 1 thankful Users Connit

11/10/2016 8:41 AM	Rate (0)
Duris_I Diamond Expert Joined: 4/28/2015 Last visit: 3/26/2025 Posts: 10837 Rating: (836)	Hello, why you don't look to TIA Help about MB_MASTER? Attachment MB_Master.jpg (501 Downloads)
	With best regards... Ivan Duris Flight: OMICO
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This contribution was helpful to 1 thankful Users Connit

11/10/2016 10:38 AM	Rate (0)
Connit Posts: 5 Rating: (0)	With my program (for the master bloc cf image), I get an error 8189. I found that post https://support.industry.siemens.com/tf/ww/en/posts/status-16-8189/126545/?page=0&pageSize=10 that sent me to that solution https://support.industry.siemens.com/cs/document/109474481/how-can-you-read-input-words-in-the-address-range-from-9999-to-65535-with-the-simatic-s7-1200-via-modbus-rtu-?dti=0&lc=en-WW but I don't know how to use the blocs coming from the library MODBUS(RTU), seems like if I just replace the blocks from the library MODBUS with thos I always get errors Attachment image002.jpg (289 Downloads)
Connit Posts: 5 Rating: (0)	Last edited by: Connit at: 11/10/2016 10:39:13 AM Last edited by: Connit at: 11/10/2016 10:41:26 AM
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11/10/2016 10:49 AM	Rate (0)
Duris_I Diamond Expert Joined: 4/28/2015 Last visit: 3/26/2025 Posts: 10837 Rating: (836)	Hello, if you want use -rtu library instructions, you must completelly rework DB blocks depended to new instructions, better delete all previous MB instructions and their DB and insert new blocks. Recompile, download.
	With best regards... Ivan Duris Flight: OMICO
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11/10/2016 2:18 PM	Rate (0)
Connit Posts: 5 Rating: (0)	OK I found what didn't work. Because the last time I used the MODBUS it was with a s7-300 with a sample program , I didn't have to use the (4) before the register address and I just understood the program and the modbus MASTER block at the same time. Thanks for the tips
Connit Posts: 5 Rating: (0)
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