1734-VHSC24 Explicit Messaging

[Guest Mark Whitehead]

Does anyone have a sample of how to write explicit data to this module? I need to write to assembly 108 but wasn't sure how to set up the MSG instruction - Message Type, Service Code, Object Type, Object ID, Object Attribute, etc. Maybe any sample to a 1734 module via devicenet would help. Thanks!

[Ken Roach 194]

Hi Mark, Which controller are you using ? Sending explicit messages is relatively easy in the Logix-family controllers, and is possible but not easy in SLC-500 and PLC-5. The 1734-VHSC user manual gives you some of the information you need to know on page 3-12, where is lays out the arrangement of the 54 bytes in Assembly 108. It doesn't give you a couple of important facts, though. You can learn a lot about Explicit Messaging from the Knowbase document G16551, which I used as a reference when writing this post. Here's what you need to know: Service = 0x10 Set Attribute Single Class = 0x04 Assembly Instance = 0x6C (108 decimal) This configuration Assembly for the VHSC. Attribute = 0x03 Assembly Data Length = 54 bytes Give that a try !