armv8-m mpu: how to mark one region with no any access?

For the ARMv8M mpu, there is only two bits for the AP(access permission), another

XN bit for executable. 

I wan't to mark a region (e.g. from 0~4096) with no any access, mainly used for NULL pointer

read/write check. For ARMv7M, the mpu has 3 bits  in AP field(RASR register), and I can select 000

to mark this region no any access, but for ARMv8M, there is only two bits in the register

MPU_RBAR,

"

00 – read/write by privileged code only
01 – read/write by any privilege level
10 – Read only by privileged code only
11 – Read only by any privilege level

"

So, how should I do with the new MPU? any advice will be appreciated.