V350-35-R2 MODBUS Communication

[UniJunior]

Hi,

I want to access throw MODBUS an V350 - 35 - R2. I attached to my V350 a communication port RS4X. First of all I'm not sure that I use the correct cable to connect my PC (on which I use a soft to simulate a SCADA request as a master) on the V350 as a slave. I use an RJ11 cable with only pin1 and 6 connected: one end is in V350 on RS4X port and the other end is in the MJ10-22-CS25 adaptor which is connected on my PC serial port. Is this correct? There is any pinout of a cable with a RJ11 and DSUB 9pin mother?

Thx in advance.

[Damian]

We first need to determine if you are using RS232 or RS485.

What are your jumper setting for the V350 port?

[Joe Tauser]

The -CS25 is configured for the middle connectors using RS232. The cable you describe with 1 and 6 is for RS485 and you must have an RS485 adapter on your PC to use it this way.

To do what you want set the jumpers on the RS4X board to RS232 and use the cable that came with the PLC. Resist the temptation to make your own RJ11 cable as the Unitronics cable actually has the two center conductors crossed, making it a null modem cable.

Joe T.

[UniJunior]

I realized the MODBUS using the cable provided by the PLC...and the port set on RS232....but I didn't realize the MODBUS link on RS485...could someone give me the pinout for a RS485 cable (RJ11 on V350 - DB male 9 pins on PC)...Thanks...

[Emil]

Pin 1 is A (Rx/Tx+) signal and pin 6 is B signal (Tx/Tx-).

Do you have built in RS485 port in PC? If so, you need ot check the speck of PCor thhe card you have installed on it for its pin out.

In RS485, signal goes direct - A to A, B to B.

[Emil]

Pin 1 is A (Rx/Tx+) signal and pin 6 is B signal (Tx/Tx-).

You can find the port pin out in Instalation guide of the congtroller. It needs to come as hard copy with the unit or you can find it in PDF format on www.unitronics.com > Support page > Technical library.

I'll recommend using our connector MJ10-22-CS66. It will make connection easier. Ask your local vendor for it.

Do you have built in RS485 port in PC? If so, you need ot check the speck of PCor thhe card you have installed on it for its pin out.

In RS485, signal goes direct - A to A, B to B.

[Joe Tauser]

I realized the MODBUS using the cable provided by the PLC...and the port set on RS232....but I didn't realize the MODBUS link on RS485...could someone give me the pinout for a RS485 cable (RJ11 on V350 - DB male 9 pins on PC)...Thanks...

I don't think you understand the difference between RS232 and RS485 - they are very different voltage levels and cable configurations. Do some research on these two hardware configurations before you try to get the PLC talking to a computer on a port that doesn't exist.

Joe T.