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Modbus Register Polling

A

Thread Starter

Anonymous

What is the maximum number of registers that can be polled at one time? Is it 125 total regardless of the number of RTUs on the network?
 
S

Steven Roach

I believe it is a 100 registers. Download the modbus protocol refernce manual (PDF) from their website, it specs the max number of registers that can be polled. Also check out the help file for the MSTR instruction.
 
J

Jinesh

As per my knowledge we can poll maximum of 255 registers for analog values using function code 4 or 3. For binary values you can poll 2040 points at a time.
 
I

Imran Rajwani

Well the number of register is limited by reply size in MODBUS. The MODBUS reply len is coded as byte length and hence can be max of 255 bytes. For 16 bit analog you can do 125 register, but for 32 bit analog you can only ask for 62 register.

Regards,

Imran Rajwani
Imperious Technology Inc
 
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