Red Lion G308 Protocol Conversion

[Bullzi]

Hi everyone,

About a year ago I built a panel for a customer that has a ML1400 and Red Lion G308 HMI. He now wants to talk to the PLC with his Yokagowa SCADA System via Modbus TCP. I have been going over the Gateway Blocks in the Crimson 3.0. It seems pretty straight forward but my experience with Modbus is limited. So if you experts could answer a few questions I would be very grateful.

1) When the Gateway block is created in the Crimson it has 16 elements per address. Example 400001.00 to 400001.15. Are each one of these elements a 16 bit word or is the 400001 the word and the .00 the bit like a N file in AB?

2) I have a few Float Registers for tank levels they want to poll. How do I put the Float into the Modbus address? I know the Modbus address is a 16 bit word and the Float in the ML is a 32 bit. Do I have to split them into 2 address with 16 bits per address? Is that just a matter of putting F8:0/0-15 in one address and F8:0/16-31 in the other? Can you even split up Floats that way?

3) Is there anyway to put HMI Tag data into a Gateway block? Most of the stuff they want I can give them from the HMI just not sure how to make that happen.

Thanks for any advice you guys can give.

 

[Kidblue]

Hi,

Not sure if you are aware, but the ML1400 (Rev B) supports Modbus TCP, which may make your task a little easier??

Modbus uses function codes to transmit different data types (eg 03 will READ an integer, 06 will WRITE an integer). There are several more and you will need to assess what type of information is needed.

Using your example, address 40001 would be the same as (say) N7:0, but can also be addressed at bit level (N7:0/0-15)

Yes, you would need to reserve 2 consecutive addresses for your Float data (but you will need to check the other device as to whether word or byte swapping is required)

There are numerous sites that will give you lots more information. Try www.modbus.org as a starter or even here http://modbus.control.com/thread/1026194580 about the float query...

Hope this helps!

Rob

 

[Bullzi]

Rob,
I was aware of that but according to the program the processor is a Series A version. I am going to have them double check it next week. I have contemplated changing it out for a B version. If I do that can I still communicate with the HMI Via Ethernet? I am using the DF1 Master via PCCC/EIP protocol in the Red Lion.

I found a Knowledge Base artical that said that if you set up the Ethernet port as a Modbus TCP port that it will still work with other Ethernet/IP devices. Just want to make sure if this.

Thanks for any and all help!!!

 

[Kidblue]

Hi,

Yes, you should be able to use the TCP stack for both your HMI protocol and your Modbus TCP interface (we have done jobs using Siemens on Profinet for the HMI and then added Modbus TCP communication for the clients SCADA all on one switch without issue).

Hope this helps,

Rob

 

[Bullzi]

Thanks for your help Rob. I played around with the COP instruction and I think I now understand how to break a Float into 2 Integers. I did notice that when I put the integers back together into a float the numbers were off a little. That is fine as I don't need very accurate numbers. It is just the tank level that they are going to read out on the SCADA system So +/- a tenth or two is fine.

Thanks!!

 

[Bullzi]

Found the problem with my accuracy. It helps to put a 2 in for the length on the COP instruction.

 

[Kidblue]

It helps to put a 2 in for the length on the COP instruction.

You tend to find it works every time then!!

You will find when working on Modbus (type) systems, that the level of you may need to to do will be dictated by whether you are (say) the Master or Slave, Client or Server. For example, most of the systems we do for one customer, we are always the Modbus Slave to their Master, and so we need to do very little in terms of READ/WRITE functions etc. Once we have established the physical link (baud rate, parity etc.) we then just map an area of data for the Master to interface with. It is then up to the Master to use the appropriate Function Codes within their controller to read/write data successfully.

Hope this helps!

Rob