Modbus

[deep6ixed]

Anyone know of a good site to learn to use Modbus?  I'm looking to move forward with PLC's and more into SCADA.  So does anyone have any suggestions on where to start. 

I was figuring with connecting the Do-More to a PC and then attempting to communicate with modbus.

[b_carlton]

Straight to the source - www.modbus.org

Another great resource www.chipkin.com/files/liz/MODBUS_2010Nov12.pdf

[BobO]

And you can also use the Do-more Simulator to talk to your Do-more PLC. Configure Ethernet or RTU server on one end, and use MRX/MWX instructions to initiate transactions. Good way to get an understanding of what what the available transactions are and what you can move from place to place.

Unless you meant 'learning...' from the standpoint of writing the protocol, in which case yes, you'll need the spec from modbus.org.

[deep6ixed]

I'm looking to learn what modbus is, how to use it, things like that.  I've self taught myself plc programming, using the HMI, very basic communications...  Now I feel that to move on to the next step would be to begin to learn how to make all these individual pieces "Talk to each other"  and since Modbus is the de facto standard I figured it was a good place to start.

Plus I don't have much in the way of financial means to buy equipment just to "learn with" I am stuck using what I have around the shop.  I have a spare GS series drive with RS232, a spare Click PLC and for a short time, 2 Do-more's until they get installed in a machine.

[BobO]

Then to learn about it, I would get the spec Bernie referred to. And to play with it your Do-more systems (and possibly the Do-more Sim). It isn't hard...that's why it is ubiquitous: simple to learn and simple to use.

[rlp122]

There are some good example programs over on the ADC site in the technical support section.