PCMusicGuy
Member
So I did another project in ControlLogix (v15.65 Redundancy) not too long ago where I had a controller tag aliased to a digital input module (IB32) sitting in another rack just for I/O. The alias was set to TS_IO:I.Slot[1].Data where TS_IO was the ControlNet network connection to the I/O rack.
This way, I didn't have to add the IB32 to the I/O configuration but would still be able to see the data. Since a different controller "owned" the I/O, it also had the added benefit that when I forced the I/O for testing, all of the different controllers (3 in total) that aliased the input card would see the forced value as well.
Fast forward to today and I'm using a similar setup. I have two controllers (v20 Redundancy) aliasing an IB16 digital input card in another rack that is "owned" by a third controller. The trouble I'm facing is that the two controllers with the alias tag are not reading the input data at all. I'm not seeing any errors on any of the modules, ControlNet is happily scheduled, and I'm kind of left scratching my head. I can go online with the controller that owns the I/O and see bits 0-6 on, but the aliased tags from the other controllers show 0 for all bits.
Now I can always just add the IB16 to each controllers I/O configuration and move on, but I'd like to understand why the alias doesn't work for this case. Other than the different modules and firmware revisions, there are only a couple of other things different between the system setups. One is that on the working system, the controller that owns the I/O is in a separate rack from the I/O. In the non-working system, the controller is in the same rack. Another is that in the working system, the controllers alias modules in the rack that don't appear in the I/O configuration, but other modules do appear in the I/O config. This means I am aliasing modules 1-7, but have modules 8-13 in the I/O config. In the non-working system, I don't have any modules at all in the I/O config. I have the ControlNet card that expands to show the back plane but nothing else.
I'd be interested to hear anyone's thoughts on why this doesn't work like I expected. Perhaps I'm doing something stupid?
This way, I didn't have to add the IB32 to the I/O configuration but would still be able to see the data. Since a different controller "owned" the I/O, it also had the added benefit that when I forced the I/O for testing, all of the different controllers (3 in total) that aliased the input card would see the forced value as well.
Fast forward to today and I'm using a similar setup. I have two controllers (v20 Redundancy) aliasing an IB16 digital input card in another rack that is "owned" by a third controller. The trouble I'm facing is that the two controllers with the alias tag are not reading the input data at all. I'm not seeing any errors on any of the modules, ControlNet is happily scheduled, and I'm kind of left scratching my head. I can go online with the controller that owns the I/O and see bits 0-6 on, but the aliased tags from the other controllers show 0 for all bits.
Now I can always just add the IB16 to each controllers I/O configuration and move on, but I'd like to understand why the alias doesn't work for this case. Other than the different modules and firmware revisions, there are only a couple of other things different between the system setups. One is that on the working system, the controller that owns the I/O is in a separate rack from the I/O. In the non-working system, the controller is in the same rack. Another is that in the working system, the controllers alias modules in the rack that don't appear in the I/O configuration, but other modules do appear in the I/O config. This means I am aliasing modules 1-7, but have modules 8-13 in the I/O config. In the non-working system, I don't have any modules at all in the I/O config. I have the ControlNet card that expands to show the back plane but nothing else.
I'd be interested to hear anyone's thoughts on why this doesn't work like I expected. Perhaps I'm doing something stupid?