Modbus Ports on Quantum 434

I will be programming a Modicon Quantum 434 in the very near future. I would like to know a little about the modbus ports on the controller.

Question #1 - I have read in the manual that modbus port #1 is suitable for a modem and port #2 is not. I haven't been able to find which of these two ports I will connect to go online with the PLC though.

Question #2 - I will be using a Cutler-Hammer PanelMate Pro for the HMI. Will I be able to connect the HMI to the unused modbust port? If not, would the modbus+ port be suitable for communication with the HMI. I have priced the modbus+ interface card for the panelmate ($630). Would it be cheaper to purchase a modbus card for the PLC rack rather than use modbus+?

Thanks

Q2: Yes

If the Quanum model you have has 2 modbus ports and a Modbus plus port, you can leave one of the modbus ports spare for connecting with a laptop, use the second to link to the C-H panelmate using modbus RTU protocol and a special cable, not hard to make up, and keep the Modbus plus port for networking.
Optionally you can buy the modbus plus card for the Pmate and be able to access it on the network but I have never done it that way personally,

Brian.

(For more detail I will have to wait until I get back to work next monday as I am enjoying two weeks vacation away from work and my handy reference manuals.)

The RS232 ports on the Quantum are identical for PC connections (9600,E,1). Port 2 defaults to these standard Modbus parameters at power up, while Port 1 can be dependent on the program parameters. If you are always using the standard parameters, you can use either port.

The Quantum 434 includes a Modbus+ port as standard. For the price of the HMI card I would use a small Modbus+ network instead of RS232 Modbus.

Why Jim?

What is the advantage of using modbus+ over modbus to the HMI?
HMI updating speed has never seemed to be an issue and because of our extensive Modbus+ network we considered it unwise to put uneeded nodes on it. So even our remote PLCs which are not currently networked use modbus comm to the HMI. What am I missing?

Brian.

Sliver said:

What is the advantage of using modbus+ over modbus to the HMI?
HMI updating speed has never seemed to be an issue and because of our extensive Modbus+ network we considered it unwise to put uneeded nodes on it. So even our remote PLCs which are not currently networked use modbus comm to the HMI. What am I missing?

Brian.

Click to expand...

I agree. I would use the Modbus+ port for plantwide hookup (monitoring, production counts, etc.), one Modbus for the HMI (if its only interacting with that PLC), and the spare Modbus with a local convience port for progam support. In a pinch, a programmer could use the Modbus+ to access remotely. Its exactly the way we shipped a transmission component assembly line that had 6-7 plcs each paired with Panelmate. Worked very well.

I also don't like to put HMIs and PLCs on the same networks if I can help it. I usually prefer a dedicated HMI to dedicated PLC port, however if the RS232 causes any type of grief (i.e. limited distance) a small Modbus+ network might be more desirable than using converters.