According to the manual, it is 5 kHz.
Βut fast counter inputs have only logos with pure DC power supply (12 / 24VDC or 24VDC).

Normal digital inputs only 4Hz.

For more complementiting, you can download the manual of Logos here:

Download manuals

Hi,

to complete the answer:

- only LOGO! without AC power supply supports fast counter.
- The inputs has to be directly connected to a counter or a Thresshold trigger

Regular Input:

Here the max. frequency depends on teh scan time of the LOGO! program. Check the manual or the LOGO! example at the Siemens LOGO! Internet page ( www.siemens.com/logo ). Here you find example how to get the information of the scantime.

Hope this helps