You can also purchase frequency doublers and use older in-place, or already on-a-shelf purchased hardware.

AutoGen_896291

It appears that 200kHz was the upper range for pulse generation from the S7 1200 series PLCs.
This thread is dated 2013 and since then it appears that the CPU processing speed has been increased in the S7 series PLCs since then, I would like to know what is the fastest frequency output available now in 2017?  I need to generate an output frequency ranging from 100kHz to 800kHz, in 1kHz increments.