I am interfacing with two Cyberwave UPS's with a quantum PLC. I am planning on using the two MB ports on the front of the processor to speed up communications. Will I have to run two cable's one to each UPS or can I daisy chain them together?

 

A Modbus network can only have ONE (1) Master. The protocol is Master-Slave. The number of slaves is limited to 247 and the electrical interface (RS232/RS585).

The Modbus Ports on the front of the PLC CPU are separate networks. So each can support one Master (The PLC is typically the slave).

It is possible to make Port 1 into a Modbus Master.

Modbus Plus and Modbus TCP/IP are peer networks and therefore you can have mulitple "master" and "slave" devices.

 

In order to daisy chain them, you'd need to use Modbus RS485. The ports on the Quantum CPU are Modbus RS232. So you would run one cable out from each port to a single device only.

 

First check the com port of the ups, if RS485 you'll need a 232/485 converter for the PLC. Use one port then and then go multidrop. For 2 drops the serial speed will be sufficient with one port of the PLC. If the serial port of the UPS is RS232 then as advised above run one cable from each port of the plc.