fernando,
I use ADC, PLCs and I have never had debounce issues with them. Usually I will bring in an input and it will then turn on a control bit, the control bit is then read via Mach. The scan times on a PLC is usually much, much much faster than mach can get around to getting it off the modbus. so, if you have fast inputs then I would send them to a Set Control bit, then when Mach reads it, have mach send back a control bit to do the reset. Another option is you could use a OneShot to capture the signal, or if you need realy fast you could use an Immediate input.