How to generate oscillator signal from arduino atemega328?

Hello and good day all, how to generate oscillator signal from arduino? I'm try to generate this signal to control high voltage transformer and triggering scr in dc-cdi circuit. Here my original Yamaha LC135 dc-cdi circuit that i re-trace from original board.

And i plan to replace the P89LPC915 with atmega328...

The RPM signal will be control the transformer and scr triggering..

Just use a PWM output set to 50% duty cycle. Once it is set going it continues.

Thank Grumpy_Mike, i able to get 240VDC, PWM pulse go to transformer oscillator control, but for trigger scr, should i used same PWM or i need to give new PWM with little high duty cycle?

Well it is hard to follow that circuit because it is not a schematic but a physical layout, therefore I can't easly see what it is doing. It looks like an ignition circuit from a car or a strobe circuit.
So assuming you want the PWM for generating the high voltage then you need to fire the SCR only at the right point. Therefore that would suggest to me that you do not connect the SCR to a PWM output.

This is dc-cdi from Yamaha LC135 that i draw back from original board, i try to replace the timing chip with arduino. Looking to the original process, pickup coil will send rpm signal in low ac signal and convert to digital first..

Then it will start giving hv circuit pulse and feed 400v capacitor. Then scr will flushed to ignition coil. I will draw in schematic and post it in here. Thank Grumpy_Mike for suggestion.

As well as using pwm you can use the "blink without delay" from the examples.