Hi,
This is a situation where you don't need to use the Charge pump facility on the G540. You don't need it as you are not driving the G540 from a parallel port. Switch it to the OFF position.
Keep in mind that the charge pump was provided due to the fact that when a PC boots, the outputs of the parallel port will twitch during bootup. This has the undesirable effect off momentarily switching on outputs such as spindle relays, and issuing spurious step signals to drives etc. By having Mach3 generate a chargepump signal when running, breakout boards cab disable outputs until Mach3 is up and in control.
Since the SmoothStepper knows when its communicating with Mach3, the chargepump signal has no use in this setup, so turn it off.
While we are talking about the chargepump signal, a note relating to using it with parallel port setups.
Under the general config in Mach3 there is a checkbox labelled "Chargepump On in EStop". You should always check this. There is no situation that I can envisage that you would want to use the chargepump for anything other than an indication that Mach3 is running.
And further, relying on the chargpump for anything else other than an indication that Mach3 is running (and not necessarily running correctly) is dangerous.
Cheers,
Peter.