Home + Limit from just 1 input pin: HAL config explained

Hey there, first post, still learning.

I have been configuring LinuxCNC 2.8 trying to understand what is happening so it wont bite me later...

When I set HOME+LIMITS on input pin 10 of parport, StepConf has put code like this in the HAL File:

I have edit to reflect my gantry y1 and y2 joints.
I now kind of understand what is happening in LUT5.

So far, I understand that:

1. LUT5 have 5 inputs and one output (IN4, IN3, IN2, IN1, IN0 and OUT) ;
2. IN4 receives the signal from the serial circuit of physical switches and is TRUE when the circuit is closed;
3. Homing operation doesn't depends upon LUT5 output, but Limit detection does;
4. IN3, IN2, IN1, IN0 are TRUE when joints 3,2,1,0 are homing, respectively;
5. LUT5 OUT is TRUE only when IN4 is FALSE and IN3, IN2, IN1, IN0 are TRUE
6. Only when LUT5 OUT is TRUE the joints limit switches input pins are TRUE (meaning a switch have been tripped)

My conclusion is that joint limit switches inputs are never TRUE because IN3, IN2, IN1, IN0 are never TRUE at the same time;

Where is my logic failing ?

Can someone explain the step-by-step events and states ocurring when a physical switch is tripped ?

Thanks guys,

Tried to edit the post and the forum editor is fighting me back, the harder I try, the worst it gets.

Hey John,

I understand LUT5.
if I have code like this:
I understand that LUT5 will only be TRUE when IN4=FALSE and IN3, IN2, IN1, IN0 are TRUE

Problem is what this logic represents in the wiring of HAL from the first post, it does not make sense to me.

hum... maybe I've got LUT5 logic wrong.
I was expecting function 0x10000 to be:

but your debug shows LUT5 function to be 0x8000 for that situation.
in fact the difference between both in binary is this:

Could you explain how did you wired sim.axis to simulate this LUT5 output ?
I'm still learning HAL and could not reproduce your screen

I have done this comparison of HAL wiring in sim.axis homing and lut5 homing+limits:
 
but don't know how to translate to simulated env.