Scraphammer
Member
I'd like to add a second HMI to this system, the original being an IC754VSI12CTD-HH connected to the CPU310 via a DB25 connector at the HMI and a DB15 connector at the com 2 port on the CPU310. The DB15 connector has a 120 Ohm resistor between the Tx+ and Tx- leads for two wire RS485 communications. The DB25 end has the necessary 120 Ohm resistor between the Rx+ and Rx- leads. For proper communications I'll need to remove the resistor in the DB15 connector, add a splitter/pass through with a resistor between the Tx leads and then the main HMI should act as one end of the RS485 drop network, the splitter/pass through as the other end at the CPU310, and I can add the second HMI as a drop of the network?