Remote Connect Modbus Scanner

[ryanAstiefes]

Programming a Scadapack 470 modbus scanner to communicate with another device using Modbus RTU all works the way I would expect except for the transaction time. RdScanTimr.Value and WrtScanTimr.Value both count down from 10 seconds than transactions resume.

In my scanner setup I used a Scan Time of 1000ms and a timeout of 100ms with three failed attempts for 5 read registers and 5 write registers which also match the default Scan/Timeout, I assume the RdScanTimr.Value and WrtScanTimr.Value would count down from the Scan Time I used in the Client Modbus Scanner Setup but like I mentioned above its a cyclic of 10 seconds. 

My question is: Why am I only scanning the device at 10 seconds and not at the specified scan rate? Is there another part I need to setup?

[Joel_Weder]

Ryan,

I'm not sure I have the answer for you, but I do have a couple of comments...

- A timeout of 100 ms on a serial connection is likely much too short. Even if the port is running at a high data rate I'd go with at least 500 ms timeout. If it's slower e.g. 9600 bps, a typical timeout is 1000 ms (1 second) or more. You may be getting a lot of timeouts.

- There are two places you can configure Scan Rate and Timeout values. You'll need to verify both:

   - The default parameters for the Modbus Server Device itself. When you create a new device, these are                Default Scan Rate = 500 ms, Default Timeout = 1000 ms

   - When you Add Scanner for a device, you can specify non-standard scan rate & timeout. Applies only for           that one scanner, not all scanners communicating with that device. 

I'm not familiar with the two timer parameters you mentioned, as I haven't seen these automatically created when I add a device or scanner. Where are they being generated? I don't even see these as outputs from a MB_SERIAL_MASTER function block.

[ryanAstiefes]

The scanner I'm using is in the backend setup of Remote Connect such as in attached picture. Maybe the route I should go is use the MB_SERIAL_MASTER function block? This is my first time using the Modbus Scanner I'm sure there are limitations that I'm not aware of.

[Joel_Weder]

The Modbus Scanner is intended to be the primary method for polling Modbus devices from an x70 type SCADAPack. The only reasons one might consider using the function block method instead are:

- If more than 150 remote Modbus devices must be polled, or...

- If you just need a very limited number of points and prefer the FB method

Have you checked the timing parameters that I have mentioned? If you have, and they are OK (remember they are specified in milliseconds!), then I suggest you contact our Tech Support team for further assistance. Make sure you send them a zipped copy of the entire application and a good description of the issue, including the RTU type, firmware version, and RemoteConnect version. Here's their contact information, if you don't have it.

SupportRO@se.com  or...

1-888-226-6876

[ryanAstiefes]

Thanks for the reply! I ended going with the MB_SERIAL_MASTER FB, it has more flexibility.