Redlion TechNote Question

[mjoubert]

Hi All,

In the Redlion Technical Note TNOI23 (G3 Operator Interfaces communication with AC Tech SCF Variable Freq. Drives over RS485).

It is stated that: Ping Holding register should be set to 25.

I would like to know How/ Where/ Why you arrive at this value?

If anyone could shed some light on this it would be appreciated.

When using a G3 with CanOpen to Lenze 9400's, or RS485 (Lecom AB Driver) to Lenze 8200' or 9300's, I can see the Ping Register Value is the drives address.

But this Modbus RTU stuff is confusing the hell out of me!!!

Many Thanks,

 

[JHarbin]

Hi All,

In the Redlion Technical Note TNOI23 (G3 Operator Interfaces communication with AC Tech SCF Variable Freq. Drives over RS485).

It is stated that: Ping Holding register should be set to 25.

I would like to know How/ Where/ Why you arrive at this value?

If anyone could shed some light on this it would be appreciated.

When using a G3 with CanOpen to Lenze 9400's, or RS485 (Lecom AB Driver) to Lenze 8200' or 9300's, I can see the Ping Register Value is the drives address.

But this Modbus RTU stuff is confusing the hell out of me!!!

Many Thanks,

The ping register is a register that you know has integer data in it. The G3 uses it to determine if the device is alive and it helps limit the time that the G3 waits to determine if the device is missing.

Typically, this is register 1, but apparently Redlion has determined that the best register to get an integer response is 25 on the first device you mentioned.

If the device doesn't have an integer register to ping, you can set it to 0, but this means timeout is much slower, and this sometimes results in no communications at all.

 

[mjoubert]

Hi,

I meant the resister I usually ping is the drive register containing the address. Eg. In the case of a 9300 or 8200 it's 9. In the case of a 9400 it's 5ea1. Should the ping register for modbus not be the drive address register plus 1 Eg. 400010 for a 9300 drive?

 

[JHarbin]

Hi,

I meant the resister I usually ping is the drive register containing the address. Eg. In the case of a 9300 or 8200 it's 9. In the case of a 9400 it's 5ea1. Should the ping register for modbus not be the drive address register plus 1 Eg. 400010 for a 9300 drive?

The ping register simply needs to be an integer register. I almost always use 1 (you don't use the prefix in this case) because most of the devices I communicate with have 400001 as an integer register. Again, in this case, I type a 1 in the ping register field.

Again, the G3 doesn't use the information from the ping register, it just uses it to determine if the device is alive - it doesn't matter what data the integer register contains.

 

[mjoubert]

Hi,

The ping register and device I.D. must work in unison. How else does the addressing work on a multi-drop system?

 

[JHarbin]

Hi,

The ping register and device I.D. must work in unison. How else does the addressing work on a multi-drop system?

The ping register doesn't have anything to do with device identification.

The device identification in Modbus RTU is the Drop Number on the device settings page when you add the device. In a multi-drop serial system, there will be multiple Modbus devices under the same 485 port. Each device will have it's own drop number.

The ping register is further down the page under protocol options, and again, has nothing to do with the Device Id number. It is simply a Modbus Holding Register that the driver can use to say "are you out there". It doesn't care what the response is, just that when it Pings, it gets a response. It uses the Drop Number as part of *every* request to actually request information from a particular device. Even the Ping request uses the Drop Number so the particular device knows that it is the one that should respond to the request. Every device must have a unique Drop Number, but if they are all the same type of device, each one can be configured in the G3 to use the same ping register.

I have done this more times than I can count.

 

[JHarbin]

Hi,

The ping register and device I.D. must work in unison. How else does the addressing work on a multi-drop system?

Going back to the particular device you are asking about. The Modbus Register that contains the Device ID (or Drop Number to use Redlion's term) is simply the register that *you* have already configured in the device itself using the vendor's software or the device's front panel input buttons if it has one.

 

[mjoubert]

Hi,

If what you are saying is true, how does the redlion know where to get the address of the devices on the network from? There is only one place to set a ping register and that is in the communications setup under the device or protocol settings.

 

[JHarbin]

Hi,

If what you are saying is true, how does the redlion know where to get the address of the devices on the network from? There is only one place to set a ping register and that is in the communications setup under the device or protocol settings.

It gets the address from *you* setting the Drop Number as I said in an earlier post. The driver doesn't go out and poll Modbus Devices to determine their Address (or Drop Number).

I have tried to explain to you that the ping register has nothing to do with the device Modbus address (remember that Redlion uses Drop Number as the field where you enter the Modbus Address or Device ID - I use device ID because you use this in an earlier post). It is simply a register that the G3xx uses to ping the device that you have already set up under the Drop Number to determine if it is alive.

If you want to make this work, set up your Modbus device (the one that you want the G3xx to talk to) and give it a Device ID and set its communications settings.

Go into the Crimson 3.0 software and configure a Modbus Universal Master on the correct communications port. Use it the same communications parameters that you set on your Field Device.

Go to the device that was added automatically (PLC1 will be the name of the first device added) and set the Drop Number to the same number that you set as the Device ID on your Field Device. Set the Ping Register to 1 (this typically works).

Test your communications. It should work. If not, either your communications settings are wrong, or Modbus Register 1 is not an Integer Holding Register. Check your device Modbus Register to be sure, but as I said, Register 1 is commonly a good Ping Register.

If you have multiple devices, continue to add the under the same Modbus Universal Master and change the Drop Number to the unique Modbus Address of the new device. Set the Ping Register to 1 because once you determine what the Ping Register is, it is the same for every one of the Devices as long as the have the same Modbus Register Map.

You can keep arguing with me, but I am pretty familiar with Modbus Communications. I have connected hundreds of devices to Crimson 2.0 and Crimson 3.0 based Redlion Devices using Modbus.

 

[mjoubert]

Hi,

Sorry, I don't mean to sound argumentative. I'm just trying to wrap my mind around it.

Many Thanks for the Posts

 

[brandoncosta]

Check out SCF Series installation & operation manual.