To connect the CompactLogix to a Modbus network, when should I use the Prosoft card (MVI69-MCM) and when shall I use the Allen Bradley card (1769-SM2)?

The prosoft card is 4 times the price of the Allen Bradley. What are the limitations of the Allen bradley card that makes it so much cheaper?

 

Angela,

I have experience with a different option to solve your problem... I've used the Digi One IAP, which can convert back-and-forth between Modbus and Rockwell protocols (both serial and Ethernet).

I've used them for applications in the field, and as components within test equipment on the bench. Very reliable and easy to work with.

The price is much less than ProSoft, also.

Hope this helps!

 

The primary difference between the SM2 and the MVI69-MCM module is that the MCM module has 100 commands per modbus master port that are stored on the module itself. The SM2 when used with something other than a powerflex drive requires that you create a MSG instruction in ladder logic for each modbus command that you wish to issue. So say for instance you have 10 devices on the network, and to get all the data, you need 5 commands. This would be either 50 MSG instructions, or you could configure the module to do all 50 commands and they are done automatically.

Additionally, the 69-MCM module can operate as a modbus slave, and contains a debug/configuration port with options like a data analyzer for debugging the communications on the modbus network.

Another cost effective option would be a ProLinx 5201-DFNT-MCM (1 Modbus Port) or 5202-DFNT-MCM4 (4 Modbus Ports). These contain the same functionality at a lower cost.

Please let us know if there are any questions.
support [at] prosoft-technology.com

 

So if I can summarize (if I understand Erik correctly):

- The ProSoft is a configurable 'smart-card' which allows you to pull info at network speeds into a separate memory without adding large amounts of RSLogix5000 overhead

- The AB card is like a ENB but for Modbus, requiring RSLogix5000 to drive it "manually" message by message with MSG blocks.

- The Digi One IAP is designed for simple block transfer of words between any AB PLC and Modbus - works either direction. However, it doesn't create it's own traffic so you need either RSLogix5000 MSG blocks or Modbus master to drive it. I also won't plan on moving more than a dozen transactions per second through the Digi, whereas I'd assume either Prosoft or AB card can handle hundreds/sec.

So each has their own pros/cons. See which fits your needs.

Regards
- Lynn A Linse, Industrial Specialist, Digi

 

The ICC ETH-1000 gateway could also be another option. It supports many simultaneous protocols such as Modbus TCP (client and server), Modbus RTU (master and slave), as well as EtherNet/IP (client and server) and CSP (client and server). All Ethernet protocols can be active simultaneously, so it can generate its own requests to read from one PLC, consolidate the data and write to another, etc. Like the Digi, it also is a lot less expensive than the Prosoft & AB products.

http://iccdesigns.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=ICC&Product_Code=eth1000

Regards,
Darrin Hansen
ICC

 

Last but not least, you may not even need the Modbus card. There is a downloadable application that lets Logix act as a Modbus slave or master through the built in serial port. Go to the AB website, click on "Tools & Resources," then "Sample Code." Type "Modbus" in the search box and hit search.

-James Ingraham
Sage Automation, Inc.