1756-DHRIO and 1771-ASB Remote Rack

scantime

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Apr 2014
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Hi all, I am in the process of updating a PLC-5 processor to a ControlLogix L72 processor. The ControlLogix processor will communicate with 4 PLC-5 (physical) remote racks that have 1771-ASB modules via a 1756-DH/RIO card. These PLC-5 remote racks were "complementary" addressed in the original PLC-5, and Knowledge Base recommends simply adding octal 10 to the complementary rack in ControlLogix to take care of this - so I think I'm good here, however I would like to know if there are any dip switch settings on the remote racks that need to be changed, or any other arcane settings I should look into for this conversion so that it is minimally invasive during install? Thanks in advance!
 
Welcome to the board, Scantime. I just converted three PLC-5 processors to L71. None of the rack dip switches changed in that system, although I didn't have to deal with complementary I/O so I cannot speak to that.

You will want to consult the 1756-DHRIO user manual for setting your RPI times in the I/O Configuation tree.

If you have any I/O modules using block transfers in those remote racks, be careful how you set these up. The conversion software may change your data tables to DINT tags which will create chaotic results. You will want to make sure you only use INT tags with your block transfer messages.
 
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If it is not too late, you may want to consider the 1756-RIO card instead.
With this card, your RIO configuration can be linked with the Rslogix5000 project.
 
RonJohn, I've done several of these upgrades where a PLC5 was replaced with an ASB module, and you most certainly do have to change the dipswitches in the chassis.

Refer to pages 97 and 98 (Section 4-1 and 4-2) of the

1785 PLC-5 Programmable Controllers Quick Reference

In my recent project, they were VME based PLC5/40V processors. The VME rack was replaced by a ControlLogix rack so no ASB was added. The remote rack 1771-ASB units were reused and those dip switches didn't change on my job.

I didn't see in the original post where the PLC5 was being replaced by an ASB. If that's the case, then I agree with you Daba.
 
In my recent project, they were VME based PLC5/40V processors. The VME rack was replaced by a ControlLogix rack so no ASB was added. The remote rack 1771-ASB units were reused and those dip switches didn't change on my job.

I didn't see in the original post where the PLC5 was being replaced by an ASB. If that's the case, then I agree with you Daba.

I've re-read the original post, and I can't see it either, so apologies to you RonJohn.

I read it quickly, and had just assumed that PLC5 processors were being removed somewhere in the system, and were being replaced by ASBs to communicate with the DHRIO module.

To clarify.... any remote I/O chassis that currently has an ASB will not need any dip-switch changes, the I/O configuration in the Logix5000 platform can work with the existing RIO set-up.

Any chassis that has a PLC5 processor installed (to be replaced by an ASB) will need dip-switch changes if it is to be used as remote I/O to the DHRIO module.
 
1756-DHRIO and 1771-ASB Remote Rack Follow up

I know this was a while ago, but I wanted to follow up so this is documented for myself and others that may run into this issue in the future. In order to get this setup to work with a ControlLogix controller, 1771-ASB Remote I/O adapter(s) and complementary addressing, I needed to:

*Setup the 1756-DHRIO as a module in RSLogix 5000 backplane, I noticed this was easier than using a RIO module, as I could drill down into the 1756-DHRIO module and add further modules, which wasn't possible with the 1756-RIO module. This is how I added all 1771-ASB modules.

*Within CH A or B in the 1756-DHRIO Module, add another module for 17711-ASB module, the Rack # (octal) in the Module Properties will be the actual rack number + 10 octal, so if it's rack 5, type in 15 here (for complementary addressing only)

*Set dip-switch settings: I only ended up having to change the 3rd dip-switch on the 1771-ASB module to "off", off was for "complementary chassis". The rest of the DIP switch settings are found in 1771-ASB module handbook easily found on web.

*Connect your "Blue-Hose". I ended up connecting 1756-DHRIO top to bottom, blue wire, bare wire, clear wire, and top and bottom terminals were fitted with a 150 Ohm resistor. Wires were opposite on 1771-ASB module, and 150 Ohm resistor was also used.

*Find your "Module-Defined" tags for the 1771-ASB modules created under 1756-DHRIO. These can be used to test toggling or programming I/O.
 

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