Resistors on mesa 7i92 input pins

Hello, I have a few situations where I'm wondering if I need, or it's recommended, to add resistors before the input pin on my 7i92 board and if so - what values?

1) a simple limit switch connected between ground and an input pin
2) a simple limit switch connected between 5v (same supply as the mesa card) and an input pin
3) on the output signals of a differential receiver IC (specifically AM26LS32)
the encoder, the receiver IC and the mesa card are all connected to the same 5v power supply. is a resistor needed between the differential receiver's output and the mesa card's input?

thank you.

Personally i never use resistors on 7i92, but it is a very good idea to use them.
I would say 150 or 220 or 270 ohm resistors should be ok, those are standard values so if you can choose go for 220 ohm.
You should wait for PCW to confirm this.

1. Yes.
2. This will not work on a a 7I92 since it has pullup resistors in its I/O pins
(it will work on a 7I92t[x] since you can select pullup or pulldown resistors on the I/O pins
and in this case series resistors are recommended also)
3. No, (but the differential input adapter ground must not ever be disconnected from the
7I92 when machine power is on)

The main issue is that if that if you have a running machine with step/servo/VFD drives,
you will have multiple volts of high frequency  ground differences between various parts of the machine.
Because of this, simply grounding a bare I/O pin to frame ground can easily damage the input clamp diodes
on the 7I92 with a negative voltage.