A2D with External clock

I have an application where I need to grab three A2D channels simultaneously driven by an external clock. The basic application is to read two sensors with the conversion clock being supplied by an encoder. Some assembly moves, which drives the encoder, and at each encoder tick three A2D channels are read simultaneously. (Two sensor and the index channel of the encoder.) I noticed that the STM32F part used for the Cerbuino type boards has the ability to drive the A2D via an external clock source, I have not looked at the datasheet for the NXP processor that the G120 uses yet to see it it has the same capability or not.

My question is has anyone else played with using an external clock with A2D on these boards? I don’t want to reinvent the wheel and start from scratch. If not I’ll delve into it and be glad to share what I learn about doing so.

It looks like the STM32F is the way to go. The NXP processor has a single 12bit A2D and has an 8x multiplexer. Since i need simultaneous samples that won’t work. The STM32F has three 12bit A2Ds. Now one to learning how to set it up for an external clock.