2.2.3 Frequency generatorWith the dialog part of the ATmega you can also select a frequency generator, which supportscurrently a selection of frequencies from 1Hz up to 2MHz. The output of the 5V signal is donewith a 680Ω resistor to test port TP2. You can use the GND signal from the minus pin of the zenerdiode extension or the test port TP1. The test port TP3 is connected to GND with a 680Ω resistor.Of course you can also connect a driver circuit to the ATmega port PB2 with a separate outputdriver circuit and a additional output terminal. But the input of this circuit should not insert a bigcapacity load for the ATmega output.