AXI Interconnect PL301 r2p3

I have an AXI master and an AXI slave connected to interconnect in my setup.

I have used AMBA Designer tool to generate Interconnect RTL.

I have a question on Tidemark :

What is the significance of Tidemark in AXI interconnect?

Why Tidemark option is included for both master and slave interfaces?

Could you please explain when Tidemark is set to some non zero value, how does AWREADY signal behaves at master end ?  

At slave interface block (master end) of interconnect , I had set tidemark =4 . I am performing back to back outstanding transactions , AWREADY signal at master end behaves as shown in the attached picture.  Why AWREADY is behaving in this way? 

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