Need help with understanding PID control

[Megahertz]

Thanks Henrik. So, is there any way I can tell what is the actual gain setting ( like 2.14 or 3.5 etc) before I multiply with 10 or 100. For example just by looking at lets say for example $0324?

I tried the following code, but my duty stays at 255 and is not coming down after overshoot.

'PROPORTIONAL VARIABLES
Error_P Var Word
Kp Var Word
'---------------------------
Kp=$0900

Main:
Gosub Get_Sensor_Value ' Get value from sensor

' ----- PROPORTIONAL CONTROL----------
Error_P=Set_Point-Sensor
Drive_p=(ABS Error_P) */ Kp
If Error_P.15 then Drive_P=-Drive_P

'--------------------------------------
Drive_T=Drive_T+Drive_P '(I used DriveT=Drive_T+... to keep some level of drive)
Duty=Drive_T
Gosub Duty_Mosfet
Pause 250
Goto Main

Duty_Mosfet:
If Duty>255 then Duty=255
If Duty.15=1 then Duty=0
HPWM 1,Duty,500
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