Want to know the Theoritical & Practical Mimitation on RS485 Modbus Communication Length & Number OF Slaves a Master Can Handle.
The limitation will come from the RS-485 network, and not from Modbus protocol run on it.
The maximum Nodes on one RS-485 network is 32. Maximum distance will depend on the applied speed as well as the cable type.
The maximum Modbus Slaves per one multi-drop network is 255.
For complete overview on RS-485 interface, you could visit :
M. Harisman harisman(AT)integrateknik.com
For MODBUS, VALID slave addresses are 0-247, where 0 is for broadcast.
The maximum also depends on the PHYSICAL network.
For RS485 networks, depending on the design, a "typical" maximum is 32 nodes, however, with proper design this can be increased. Also, buffer transceivers can be used to extend the network.