How to control Relay using EMC2?

Hi, everyone:
How are you doing!
I am doing a project using EMC2 to control four stepper motors and three relays.
I use G-Code to control linear motion of XYZA axis. When X axis arrives at certain position, the relays has to be enabled, which means has to receive a voltage more than 3.3v(1 logic).
Pin2 to pin9 is used to control the three axises, pin1,14,16,17 could be used as output which is enough.
The question is how to output logic 1 when G-Code run to a certain line?
Any help is appreciated, thank you!

Regards
Joe

linuxcnc.org/docs/html/gcode_main.html#sec:M62-to-M65

Thank you very much!
I am reading the materials.