Last Chassis on RIO

Another question for the RIO experts. SW3-4 on the 1747-asb module is for last chassis. Can there be two chassis setup for "last chassis" on the RIO link? Would I set my newly added chassis as last or leave the original as last? (Still reading and learning, thanks for the help)

I'm not sure, but I think that the "last chassis" selection simply inserts the termination resistor for you. It connects it across the blue hose conductord on the card, somehow. That way you don't have to connect one yourself.

So. the chassis physically located at the end of the blue hose should be the only last chassis.

I used a moto-man RIO card that did the same thing with a jumper selection.

Okay, "Last Chassis" is kind of a wierd thing. On A-B adapters, it does not switch in a terminator.

Nor does it mean that the adapter is the highest-numbered Logical Rack on the RIO network.

What it means is that the adapter is the last fractional-Rack device in a Logical Rack that is composed of more than one adapter.

If your devices on the RIO link represent Full Rack devices, you never use the Last Chassis switch.

If you have fractional-rack devices, you turn on the Last Chassis switch for the last fractional chassis device.

For example:

1794-ASB Rack 03, Group 00, 1/4 Rack
1794-ASB Rack 03, Group 02, 1/4 Rack
1794-ASB Rack 03, Group 04, 1/4 Rack <Last Chassis>

1794-ASB Rack 04, Group 00, 1/2 Rack
1794-ASB Rack 04, Group 04, 1/2 Rack <Last Chassis>

1771-ASB Rack 05, Group 00, Full Rack <not Last Chassis>

At least, that's how it was explained to me.

I think maybe this applied only to PLC-2 RIO scanners and that the switch is immaterial with PLC-5 or 1747-SN scanners.