Has anyone used the "Logix5000 Controllers as Masters or Slaves on Modbus" application solution from Rockewell (Publication CIG-AP129A-EN-P)? It is slightly confusing in that it tells you it ONLY supports Modbus RTU, but then the user protocol is ONLY ASCII. I just want to make sure this is going to work. It is a heck of a lot cheaper then adding a Prosoft card.
Modbus w/Logix controllers
- Thread starter jedft
- Start date
nwboson
Member
I've used the 1769-SM2 module to drive the Modbus RTU of AB drives. I have not driven directly from the com port though - kind of a bummer to lose your backup programming port.
With the 1769-SM2 I just followed the documentation and had no problems - it was so easy I can't even remember how it works. That app solution looks ugly (like most com programming on the AB's) - good luck
With the 1769-SM2 I just followed the documentation and had no problems - it was so easy I can't even remember how it works. That app solution looks ugly (like most com programming on the AB's) - good luck
Contr_Conn
Member
Jedft:
First, make sure you use application v2 that distributed with v17 or higher. V2 is also availabe in the Knowledgebase
Modbus serial has to flavors:
RTU - 8 bit protocol and ASCII 7 bit protocol that is not used anymore
Logix supports RTU only
To use Logix serial port you need to switch it to the "USER' mode that supports only "ASCII" protocol that has nothing to so with Modbus ASCII - just the same name.
Just load applicaiton and it will work without any modifications.
First, make sure you use application v2 that distributed with v17 or higher. V2 is also availabe in the Knowledgebase
Modbus serial has to flavors:
RTU - 8 bit protocol and ASCII 7 bit protocol that is not used anymore
Logix supports RTU only
To use Logix serial port you need to switch it to the "USER' mode that supports only "ASCII" protocol that has nothing to so with Modbus ASCII - just the same name.
Just load applicaiton and it will work without any modifications.
Greg Dake
Member
I have one application out there where I have a ML1100 and two VFD's communicating via Modbus RTU out of the ML1100's serial port. It's been in service for about 4 years and hasn't hiccuped since.
Greg
Greg
kittydog42
Member
I have successfully used a CompactLogix as a Modbus RTU master through its own serial port. I used a Red Lion ICM5 RS-232/RS-485 converter to communicate with 3 or 4 slave devices. The sample code they provide was hard to understand but I locked myself in a room for a day and figured it out. One annoying thing about the sample code is that it is written for a ControlLogix processor, so if you have a lite version of the software you may not be able to open it and convert the processor. I had that problem at the time but can't remember how I worked around it.
Ken Roach
Lifetime Supporting Member + Moderator
Let's take a step back:
Which CompactLogix controller model are you using ? I figure it's one with ControlNet or with only serial if you don't have Ethernet.
Do you need to have the CompactLogix be the Modbus Master or the Modbus Slave ?
What are the external devices the CompactLogix needs to communicate with ?
I've used both the example code and the Prosoft MVI69 module. For reliability and performance I strongly prefer the Prosoft module.
Which CompactLogix controller model are you using ? I figure it's one with ControlNet or with only serial if you don't have Ethernet.
Do you need to have the CompactLogix be the Modbus Master or the Modbus Slave ?
What are the external devices the CompactLogix needs to communicate with ?
I've used both the example code and the Prosoft MVI69 module. For reliability and performance I strongly prefer the Prosoft module.
Ken, It's the 1769-L31 Dual Serial. We are trying to talk through a serial Radio to an iFix SCADA system. The controller will be a Modbus Slave.
Now we are looking at the Red Lion Data Station to do the conversion.
Cost is a serious consideration, but at the same time it has to work. That A-B application guide/example code is apparently quite misleading. Their tech support told us they have had 4 other calls this week telling them this doesn't work as they described in the guide.
Now we are looking at the Red Lion Data Station to do the conversion.
Cost is a serious consideration, but at the same time it has to work. That A-B application guide/example code is apparently quite misleading. Their tech support told us they have had 4 other calls this week telling them this doesn't work as they described in the guide.
OkiePC
Lifetime Supporting Member
Why not use the iFix driver for Allen Bradley DF1 instead of Modubus?
Ken Roach
Lifetime Supporting Member + Moderator
I've made calls to Prosoft insisting their device didn't work as described, too.... . until I found the mistakes I made.
If your application is straightforward, like reading a block of 4xxxx addresses and writing another block of them, I say use the Modbus code. Since it's using radiomodems it's likely that they are extremely forgiving of inter-character framing delay.
Download ModScan32 as a test client, and give it a shot.
If your application is straightforward, like reading a block of 4xxxx addresses and writing another block of them, I say use the Modbus code. Since it's using radiomodems it's likely that they are extremely forgiving of inter-character framing delay.
Download ModScan32 as a test client, and give it a shot.
nightline
Member
I've tried this to,but it gives you so many programming trouble.
I've chosen for a Ethernet version of the CompactLogix, add an Anybus Communicator and your realy easy up and running with your ModBus.
If your communication is time criticall, please forget the serial port on a CompactLogix, I used it for DH485 communication to a servo system, and it was much to slow ( bit cycle time of about 0,4 sec. ).
I've chosen for a Ethernet version of the CompactLogix, add an Anybus Communicator and your realy easy up and running with your ModBus.
If your communication is time criticall, please forget the serial port on a CompactLogix, I used it for DH485 communication to a servo system, and it was much to slow ( bit cycle time of about 0,4 sec. ).
Gee, I wish someone has told me that before I wrote my Modbus ASCII driver (just a few months ago).
If you are going through modems (where there might be a short delay in transmission), then ASCII is the way to go. Any break in a RTU packet could be interpreted as the end of that packet (which would then be rejected).
Because ASCII uses a colon (":") for the start, and a CR/LF pair as the end of a packet, any delays in the packet (to a point) will be ignored.
http://www.lammertbies.nl/comm/info/modbus.html
And before someone says that nobody uses modems anymore, we just set one up for a client last week.
Will AB 1769-L32e communicate to a serial device set for Modbus protocol via RS232
Have a Allen Bradley 1769-L32e CompactLogix PLC and would like to use it to communicate to a DeltaV Serial Card- not programmable type. Will the 1769 communicate via the MODBUS RTU protocol correctly through it's Serial Port to the Serial Interface set as a slave device? THe DV Serial Card set as Master?
Have a Allen Bradley 1769-L32e CompactLogix PLC and would like to use it to communicate to a DeltaV Serial Card- not programmable type. Will the 1769 communicate via the MODBUS RTU protocol correctly through it's Serial Port to the Serial Interface set as a slave device? THe DV Serial Card set as Master?
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