500KHz能用环形振荡器产生吗？

OK,
You can use capacitor between two stages to slow donw the oscillation frequency

当然可以了，，而且也是比较简单的！

ring osc's frequency is usually high( MHz range), so, it is not suitable to be used as kHz osc, you can use relaxation osc to generate the 500kHz frequency.

using ring osc to produce 500khz waste a lot power. u can use it to generate frequency in MHz range and use clock divider to get 500khz from it

环振后用分频器...会不会误差比较大啊?

relaxation osc is the best choice

or multi-vibrator

ring oscl + divider