This question was raised in the 'How to implement a secure IoT system on ARMv8-M' webinar, view all the questions in the round up blog post.
The Secure Attribution Unit (SAU) is within the processor. The Implementation Defined Attribution Unit (IDAU) is outside of the processor. As explained in the presentation it is the highest security setting defined by the SAU or IDAU that determines the security state of an address. In addition to the example memory map diagrams shown in the webinar slides, there is a further written explanation available from the ARM Developer site.
Your link doesn't go anywhere (any more?). Could you kindly re-post?
Hi Andreas,
Try this link on SAU and IDAU.
Thanks Mike. Nice to hear from you! (I wasn't able to explain the difference as clearly as you guys could. Thanks for the assist! But there's one answer I couldn't find -- is there any restriction that is imposed on the IDAU by the existence or construction of the SAU?)