Modbus RTU (RS485) Check Network Status

[Steveo]

Hi All - I have two V570's configured with Modbus RTU (rs485) for COM Port #2 on both units.  I used the Modbus master/slave examples and the read/write functions work fine.  My problem is that I when I use the Check Network Status for the slave under Communication and OS it times out and returns a red, fail status.   Everything I have read gives me the impression I should be able to use the master as a bridge to the slave unit for downloading projects.   Is this possible over Modbus RTU?  If so, what am I missing?  Thank you for any help.

Here is my Setup:

PC directly connected to USB port on Master v570.

Master v570 Port 2  connected to Slave v570 Port 2 with 6 wire cable.  Units are sitting on desk 2ft apart for testing.   Jumpers are set to rs485 with termination on both units' Port 2.

Attached are the master/slave projects:

 

 

 

Modbus485 Master.vlp

Modbus485 Slave.vlp

[Ausman]

Hi Steveo, I didn't even look at your .vlps, as 2 things stand out.

 

3 hours ago, Steveo said:

Master v570 Port 2  connected to Slave v570 Port 2 with 6 wire cable. 

6 wire?  Aren't you just using 485?

 

3 hours ago, Steveo said:

master as a bridge to the slave unit for downloading projects

Also, why not just use the Canbus ports?  Dead easy and much faster.  You can have both types of comms going concurrently.

cheers,

Aus

[Ofir]

Hi,

There is no option to use bridging over USB.

Basically if you wish to perform bridging over RS485 , the PC must be part of the RS485 network but... the PLCs cannot be configured to MODBUS. (the serial port should be configured to PCOM - default protocol).

As Ausman mentioned above you can connect both PLCs using CANBUS and connect the PC to one of the PLCs using RS232 or Ethernet and perform the bridging.

 

[Steveo]

Thank you for the info - will use CANBUS between them.

[Ausman]

And when I said use Canbus, forgot to add that you should be implementing the UniCAN system.  Lots in the help files.

cheers,

Aus