Today is...
Wednesday, June 20, 2018
Welcome to, the global online
community of automation professionals.
Featured Video...
Featured Video
EtherCAT with CTC’s master lets your multivendor network play well together...
Our Advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive
Hakko Modbus tables
Turning off a Hakko screen changes the table select register $s800 to 65535.


I am using the Hakko V706MD HMI with a DU01 ethernet expansion and am having problems using the Modbus tables. As you may know you need to set $s800 to the value of the modbus table that you are using (there are 255 tables). We are using Kepware as the master and the Hakkos as the slaves. If a machine goes down (power fail, etc.) the $s800 reg goes to -1 (65535) and all of my devices that are in modbus tables go bad. I can do a synchronous write in the kepware OPC quick client and move 0 into $s800 (which is the table I am using) but the values remain bad until I close the client and reopen it. This also happens in Excel if I loose the data due to $s800 <>0 then I write 0 into a DDEpoke VB command (which changes $s800) but the data doesnt refresh until I close Excel and restart. I have tried to update links in the Edit-link tab but that doesn't work. All of the data coming from the Hakko $u and $s registers is correct on start up it is only the PLC data that I have on the Modbus tables that doesn't refresh. Any help would be most benificial.


Hi Darren,

I have seen this issue and I am trying to get Hakko to change the default from -1 to 0. This would resolve that issue.

If you want to contact me directly to discuss the application, please feel free -
edbrown AT monitouchhmi DOT com

Best regards,
Ed Brown
Technical Support Manager
Monitouch HMI

This is an update for this problem. We have had a lot of discussions with Hakko and they are very helpful. Their engineers have changed the software for us so that now if you have only one modbus table used the machine will default to that one (regardless of the value in $s800). Now if one of our machines goes down it instantly starts modbus comunication when it is restarted.

Another change that they have made is when you now select the "system setting" "unit setting" "IP address" and change the IP address that you want on the project. The address on the transfer program page changes also to the same address.

The new software is available in Jan07 I have been trailing a prerelease version to see how it goes.

To make the new changes happen you have to make sure that you download the program not just the screen data into the Hakko, on our V706MD the version is 1.637 now with the changes.

Hope this can help someone