Hi,
I used Mach3 for some years, firstly with a parallel port and then an Ethernet SmoothStepper (ESS). For the last eight years I've used Mach4 and an ESS.
To my knowledge there is no pin#18, or rather a correction, the parallel port on which all of Mach3s and Mach4s port and pin numbering derives from the DB25 socket,
in a parallel port DB25socket pin 18 is an earth.
I have attached a pic of the 26pin IDC socket employed by the ESS which has identical numbering to the DB25, expecting pin 26 of course. That is to say the ESS ID26 socket has
identical signals and numbering to the DB25.
As you can see pins 18 through 25 are all earths. To whit you have shown the Port and Pin Assignment tab of the ESS plugin tab.....and there is no signal pin 18.
In normal mode, that is pins 2-9 as outputs, the most common parallel port configuration;
pin1=Output
pins 2-9 =Outputs
pins 10-13 =Inputs
pin 14=Output
pin15= Input
pins 16-17 =Outputs
Again no pin 18.
Craig