What is the maximum permissible frequency that a digital input of the MV210 DIGITAL INPUT MODULE can handle in case of using this input to read an impulse signal?

It depends on variant of device : MV210-202 (measuring frequency up to 100 kHz), MV210-204 (measuring frequency up to 400 Hz), MV210-212 (measuring frequency up to 100 kHz), MV210-214 (measuring frequency up to 400 Hz), MV210-221(measuring frequency up to 400Hz).