Auto tool change my M6 command

Hello!
I'm new in HAL and want to create auto tools change procedure.
I have arm and turret with 20 tools.
arm and turret driven by servo.
I've fount in Integration Manual some code for my purpose:

net tool-number <= iocontrol.0.tool-prep-number
net tool-change-loopback iocontrol.0.tool-change => iocontrol.0.tool-changed
net tool-prepare-loopback iocontrol.0.tool-prepare => iocontrol.0.tool-prepared

I undersand that:
the "wire point" tool-number connected in build in point iocontrol.0.tool-prep-number
then created variable "tool-change-loopback" and connected to butild in iocontrol.0.tool-change, wich itself connected to the point
of end procedure iocontrol.0.tool-changed?
All I need to create my own "tool-change-loopback" function and describe it.
Am i right?
Can anybody help me to make auto tool change (M6Tn command) that it works so as in obviosly CNC.
Thx