cc2538 memory protection unit

No, there is no memory management unit in a CM3 core.

Regards,
/TA

To start with Zigbee Home Automation, you can download and install Z-Stack Home 1.2.1. There are lots of documents in the Documents folder. You can start from Z-Stack Home Sample Application User's Guide.pdf and Z-Stack Home Developer's Guide.pdf

You can refer to section 1.3.1.6 and 3.2.4 MPU in CC2538 user's guide.

1.3.1.6 MPU

The MPU supports the standard ARM7 protected memory system architecture (PMSA) model. The MPU provides full support for protection regions, overlapping protection regions, access permissions, and exporting memory attributes to the system.

There is no RTOS in Z-Stack. It use a tiny OS that run every task in round-robin.

Do you check Chapter 3 of Z-Stack Home Sample Application User's Guide.pdf?

Examples of Z-Stack Home can only be built by IAR.

As I know, it doesn't support antenna diversity.

Yes, it is possible. But, you have to do it by yourself.

But how is it possible?

Its written in section 3.2.3 of Z-Stack Home Sample Application User’s Guide, where it uses 3 devices.

Is there a customize and buy option available for the modules inside CC2538 development kit?

I say it is possible but need to do it by yourself, which means you have to revise and merge sample Thermostat and sample Heating Cooling Unit into one example.

You can buy them from Digi-Key , Mouser or TI e-store.