MARK VI Serial Modbus Communication


Thread Starter


Hi All

In our site we have two gas turbines with MARK VI control system, the communication with DCS is through MARK VI HMI serial Modbus. The Modbus cable is connected between HMI MARK VI and serial Modbus cards in YOKOGAWA DCS panel. Means the communication is established from HMI MARK VI .

Now I want to add some signal in MARK VI to communicate with DCS. Could you please provide to me some instruction how I can do it?


GE used several methods to communicate via MODBUS over the product life of Mark VI. One used TCI and another used CIMPLICITY.

The HMI communicates with the Mark VI using EGD (Ethernet Global Database), and any signal that is communicated to the DCS must first be available via MODBUS--meaning it must be configured in Toolbox to be on an EGD "page."

Do you know if the signals you want to add to MODBUS are already on the EGD? Or will you have to also edit the .m6b file to add them first to an EGD page?

Do you have the password(s) for the various Privilege levels in Toolbox to edit the .m6b file, along with the experience to add signals to the EGD?
I could help you more in a Mark VIe/WorkstationST system, where what you're asking takes about 2 seconds.

Unfortunately, in the Mark VI era it was a little more work, and also a little before my time so I'm not an expert. I can point you to GEI-100517A "Modbus for HMI Applications" which goes into details of the TCI configuration files.

It boils down to making sure the signal you want is on EGD (from Toolbox), making sure it is available in the Cimplicity point database, and then making sure TCI is configured to provide the data over Modbus to your DCS. All of this assumes you're using a GE provided HMI setup in a typical way.
Dear Sir;

The signal is already exist in EGD, and I know all password. I want just to add this alarm (signal) to list of Modbus signal to DCS.

Dear Sir;

Could you please tell me where I can get GEI-100517A "Modbus for HMI Applications."

You could ask GE, but its faster to Google GEI-100517, second link. :)

It might also be installed from the eTCSS CD somewhere on the HMI, but I don't have one sitting around to check.
I just entered 'GEI-100517.pdf' (without the quotation marks) into my preferred World Wide Web search engine (which is NOT Google, by the way), and was taken to several links to be able to download GEI-100517.pdf. (I also don't typically use scribd, because they want to charge for the privilege of downloading documents which are available for free from other sites...).

Sometimes Google returns more (and sometimes more relevant) search results, but it's never my first choice when searching the World Wide Web for anything.

SOMETIMES, adding a signal to MODBUS is as easy as editing MODBUS.DAT on the GE Mark VI HMI, and then re-starting the HMI. Find a spare holding register or holding coil and change the name to the signal you want to add. (I would probably choose a spare holding coil, rather than trying to edit the proper bit of a packed holding register--but that's just me. I'm a MODBUS simpleton--and want to remain that way.) That works MOST of the time. BUT, be aware--GE is consistently inconsistent in their use of many "features" and the standard with most GE control systems of late is: There is no standard. And that is magnified many orders of magnitude if GE Belfort (France) had anything to do with the configuration/programming of the units.

If you successfully edit MODBUS.DAT (it's usually in either the root directory of F: drive; sometimes it's in the unit-specific directory (F:\UNITn, where 'n' is the number of the unit (so, 1 or 2 at your site with two GTs--usually...)) and get the MODBUS Master to get the signal from the HMI after re-starting the HMI, then you probably want to open a command line session, change to the directly where you edited MODBUS.DAT, and run MODBUS_L from the command prompt, to create a new MODBUS.LST--which will have scaling information and many MODBUS-literate people find useful when troubleshooting.

BEFORE you edit MODBUS.DAT, or before running MODBUS_L, <b><i>make back-ups of the two files!!!</b></i>

Hope this helps! Please write back to let us know how you fare!

I assume from the above conversation that you guys are definitely using Mark VI HMIs? i.e. configuraitons with .hmb files?

Any chance that you are using ControlST/WorkstationST HMIs (.tcw files) with your mark VI system?

Like Demi and CSA said, Mark VIe HMI Modbus is easier. I apologize for your future troubles.