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I am new to Modbus RTU, and I'm being tasked with writing some Modbus RTU protocols in a Siemens PLC
First of all,
I am using RS485 Modbus RTU.
I am confused about the difference between a node and a slave.
I have read multiple places conflicting information about how many and what they are. Some say node limit 32 some docs say slave limit 254. I don't understand the difference and need to know the max.
For exmaple, I am trying to talk with many field instruments. They have registers that i would like to poll for information. Can i have 32 of them or 254 of them??
Also,
According to some other docs i have read, i have seen the term register number and data address. What is the difference?
When someone says register are they simply saying hey that is register number 1, 2, 3, 4, etc., and its address is 0001, 0010, 0011, etc.?
Or does data address mean something else?
In this link below i found some information that is causing the confusion.
https://www.schneider-electric.com/en/faqs/FA168406/
It says register number and data address. But for the data address the range is the same for all the registers. Shouldn't the range be restricted for certain registers?
For example: coil registers get this range and so on for each type.
any help is much appreciated.
First of all,
I am using RS485 Modbus RTU.
I am confused about the difference between a node and a slave.
I have read multiple places conflicting information about how many and what they are. Some say node limit 32 some docs say slave limit 254. I don't understand the difference and need to know the max.
For exmaple, I am trying to talk with many field instruments. They have registers that i would like to poll for information. Can i have 32 of them or 254 of them??
Also,
According to some other docs i have read, i have seen the term register number and data address. What is the difference?
When someone says register are they simply saying hey that is register number 1, 2, 3, 4, etc., and its address is 0001, 0010, 0011, etc.?
Or does data address mean something else?
In this link below i found some information that is causing the confusion.
https://www.schneider-electric.com/en/faqs/FA168406/
It says register number and data address. But for the data address the range is the same for all the registers. Shouldn't the range be restricted for certain registers?
For example: coil registers get this range and so on for each type.
any help is much appreciated.