Total # of Modbus Transactions

I understand this unit will only handle a total of 64 transaction. Which is actually not very many! But I am reading in the product manual and it mentions creating “Arrays”.

I understand “Array’s” , but don’t understand how they would work in setting up the transaction. So let me try to provide an example, and maybe you can explain.

I have a modbus address that I am reading, it is for “Temperature” the address is 3 using a function code of 03. Now I want to read this exact same address from 3 different servers (server1-, (Server2-, (Server3- can I create an array for this that would only equal 1 transaction? If so can you explain how I should do this.



You are limited to 64 slave devices not transaction. Each slave is set up separately with its own set of transactions. There is no limit to the number of transactions but you are limited by 4KB of IO data.

In your example you have three slave you would be able to set each slave up to have a transaction reading holding register 3. To create an array, you would read multiple registers. For example you could do read holding registers starting at register 3 for 10 registers. (fig 1) Then when configuring the tags, you would collapse them to make an array. (fig 2&3)
(fig 1)
(fig 2)
(fig 3)