#27 - Rockwell PLC using Produced and Consumed tags

In a Rockwell CPU the tags can be of the type Base, Alias, Produced and Consumed. 

In this post we will show an application of the types Produced, which is a CPU tag configured to be Consumed by other CPUs, and Consumed, which is a tag that receives data from a Produced tag from another CPU at an RPI frequency. configured (scheduled data). 

A practical application of the use of this type of tag, is for the communication between PLCs in the same network (backplane, CNet, DNet or Ethernet-IP), when it is necessary to have a form of "handshake" between them, being able to indicate Flags, as for example, a failure in any of the modules, the current state of a process, among others. The advantage of using Produced and Consumed tags, instead of Messaging, is due to the fact that it is a multi-cast communication so the configuration is significantly simplified.

We set up a network with 3 PLCs and 4 IO cards in RSLogix Emulate 5000, where the PLC in slot 2 has two IO cards in slots 3 and 4, the PLC in slot 5 there is an IO card in slot 6 and the PLC in slot 7 there is an IO card in slot 8. In this example the PLC [2] is the Tag Consumer and the PLC [5] and PLC [7] are the tag producers.

We created the tags on the PLCs, configuring the properties of the tags with type Produced and Consumed:

Testing this online communication between PLC Produced> Consumed:

Some additional notes:

• The CPU produced must be inserted in the IO configuration list of the consumed CPU
• The source tag name must be the same as the produced tag name on the CPU produced
• Data types can also be of the UDT type. UDTs are recommended to reduce the number of connections, increasing the efficiency of the PLC.
• The maximum memory size is 500bytes per connection