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Can I write in an Input Register? Modbus
发布于 2020-08-09 16:18:52
I've been working for 2 months in a MODBUS project and now I found a problem.
My client is asking me to write in an input register (Address 30001 to 40000).
I thought that was not a thing for me because every modbus documentation says that 30001 to 40000 registers.
Is it even possible to write in those registers? Thanks in advance
Questioner
Rauññ
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12
Your answer helped me to find what I was doing wrong. As you said, there are 65536 input registers. The restriction of being between 3xxxx and 4xxxx is just a convention... they can do whatever they want. So I'm able to write in 30120 using function fx03. Thanks!
If you say that a 3xxxx address is a Holding Register I and many others would say that you are wrong.This has a cleaner solution. Schneider, the current owner of Modicon, and other manufacturers too, to exceed the 9999 register limit now use 6-digit addresses like 4xxxxx instead of 4xxxx, so there is no need to skip Modbus addressing rules. In the last Modbus driver I wrote I also used 6-digit addresses
I agree with you Lluis. But this is my very first project using Modbus and I didn't develop the slave... I was given a set of addresses I have to read/write and If they don't want to follow the Modicon protocol is not in my hand... And belive me it sucks because it took me more time to realize what they were asking for. Modicon protocol should be followed by everyone