Modbus Addresses

[Combos]

Hi everybody!

I'm trying to connect a JUMO oven controller to labview using a RS485 serial connection and Modbus RTU. I have the NI Modbus Library which has been very helpful except for a few things. Specifically, some of the addresses within the slave are very straight forward and are just a hex number I have to plug in but some of them are shown as having an additional address that goes to the individual bits (See attached picture). Are these coils or input registers or something? And how do I read them in when the Modbus library only allows me to input one address? Please help!

Thanks!

[Tim_S]

What you have circled in red would be the bit in the word you'd read. The address is 0x0026, though that may not be the actual address; you may have to hunt around for the actual starting address.

[ShaunR]

You read the address then mask (and) the bit you are interested in to get that state. You will notice that the bits are 2^n so each bit represents the state of an output/input. So to get the state of "Control Contact 4", read the word at 0x026 then AND the result with 0x8. If it is greater than 0 (1), it is on; 0 it is off.

[Combos]

Thanks guys this helps alot!