CC2538: ZNP, ZED Sleep mode, how to communications with the microcontroller/pc?

Hi

Using Z-Stack 3.0.2, I've turned the power saving feature on for ZNP ZED and enabled CTS/RTS.

I'm using Z-tools to communicate with the cc2538 module.

And it goes to sleep once joins a network. And I could see from the sniffer that it polls data every 4 seconds because I've set it to 4 seconds.

But it stops talking to the UART, and both CTS and RTS are asserted low.

Z-tools was definitely working over UART because I use it to set up the joining into the network.

I thought CTS/RTS would sort out the communications when the ZED goes to sleep.

How do I talk to the ZNP ZED when it goes to sleep?

Ultimately I want my micro-controller to talk to the ZNP ZED over UART. I will also be putting the microcontroller to sleep, and need a way to sync the ZNP to the micro-controller.

Cheers

Harry