Interface signals for .hal files and PLC programm

Hi everyone.
I am new on Linux CNC but I am usual with CNC machines and CNC controlers. I used to work for a machine tool builder implementing Siemens, Fagor, Heidenhain, Fidia and others brands of CNC.

I am finishing my first and second projects but I have a few doubts.

On the other controls that I have used, we have a list of interface signals between the PLC and the CNC. Once we have the hal files on the Linux CNC, I think we can create the link to the linux cnc signals to be used on the PLC if needed. But still I have nbot found a list of the Linux interface signals that can be used on the hal files to be linked to the PLC.

In this particular case, I need to switch on a relay whenever the spindle will run with M3 or M4.
I also need to implement the oriented stop  on the spindle for an automatic tool changer (what I am studying how to do it on the Linux CNC).

I will be very thankfull for any tips, documentation or comments on those topics.

Thank you all in advance.

have you seen this?
linuxcnc.org/docs/stable/html/config/core-components.html

Hi there.
I figure out how to implement the M3 and M4 command to the PLC. I am working on the M19 and the tool changer.
Would anyone have any examples on automatic tool changers? I do have a fixed position 21 positions disc as a magazine.
Z movements will engage the tool on the spindle.

Any tips will help.

Hi there,I checked the link you send. I found it very useful. Thank you.
However, the signal "spindle.N.orient" that I think I have to use seams to do not work.
The N I believe is my spindle number. Once I have just one spindle, I belive N should be 0 or 1.

But now I think I should use 9 once in my CNC.ini PNCCONFIG make the configuration like:
#********************
# Axis X
#********************
[AXIS_0]
TYPE = LINEAR
HOME = 0.0
FERROR = 10.0

....
#********************
# Spindle
#********************
[SPINDLE_9]
P = 0
I = 0
D = 0

Thank you very much. I will try again with 9.

"spindle.N.orient" - (out,bit) Indicates start of spindle orient cycle. Set by M19. Cleared by any of M3,M4,M5. If spindle-orient-fault is not zero during spindle-orient true, the M19 command fails with an error message.