MSG questions

Questions about the MSG in logix 5000;

Ok, so I have to do a explicit instruction over DeviceNet.
So I am looking at the manual for the particular device and it says to do a Service 4B (Hex) class 3 instance 1 no attribute and send a data type of STRUCT which in reality is a INT. (8 bits wide).

So I set up a MSG with CIP Generic Serice type Custom and plugged in the values. I noticed that if I left the Attribute blank it would default to zero.
So is 0 the same as "none" in this type of instruction?

Also I understand the Source element and source length purpose and I am confident I have that right but the device's instructions did not specify a Destination tag., so I left that blank. Logix 5000 seemed to be OK with this, or am I missing something?

This Service Type Custom is not as clean as Get Attribute Single or Set Attribute Single which I have more experience with.

Thanks

In this case, Attribute = 0 means that the message will not include an Attribute value.

These things can be a little tricky; CIP Class 0x03 is the DeviceNet Object, right ? What are you trying to get the device to do ?

Ken,
I have to set a bit in the gauge from 0 to 1

Thanks
Joe

Ken,
So I have to set a bit from 0 to 1 to put the gauge in a certain mode.
I think I have it all figured out with the exception of what to do with the Destination tag.
I'm thinking that since I am using a Custom service type I have the option of using, or not using one as the device requires. Logix 5000 complied it fine.
Thanks
Joe

Ken,
I've been setting this up on the bench and running experiments and here is what I found.
If you use the Service Type of custom, you must add a tag to both the source and destination blocks. The plc will only ever use one or the other, but they must both be there. Did that and never had a issue after that.
Thanks
Joe