Crystal oscillator and PLL?

I wondered whether it is possible to use a TTL-clock-signal on XTAL1 for the internal PLL of the NetARM+50-3. In the Net+50/20M Hardware Reference p.130/556 it is shown, that the PLL is disabled by not using a crystal. Thanks! Chris

There are two ways that you generate the system clock: 1- Ext. osc. hooked to XTAL1 directly. For this you have to disable the pll by asserting the PLLTST* pin active low and pll active. 2- A Crystal of 18.432MHz hooked in between XTAL1 and XTAL2 while pll active.