MicroLogix 1400 PWM output

I have a ML1400 BXBA. I wire the 24V to th VDC2 and 0V to the Com2. And I tried to produce a square wave of 50% duty cycle with frequence 100Hz. My DC drive cannot read the signal. So I checked with the meter, the waveform is not sqaure and the Vrms is almost 0. When it is like 5Hz, the voltage is higher. The Vrms should not affected by Freq. So do I have a faulty PLC?

Which function are you using to generate a pulse (PTOX or PWMX)?

In your PTOX or PWMX Function File, the second line "OUT - Output" must be set to "2" to make the functions use the Output "VDC2".

For the PWMX function, you need to set the "OF" PWMX Output Frequency parameter, otherwise the frequency will default to "0". Also set the "DC" PWMX Duty Cycle ("500" for 50% ON time, 50% OFF time).

When in doubt, upload a copy of the MicroLogix 1400 Programable Controllers Reference Manual, then go to Chapter 6 "Using High-Speed Outputs", Page 114.