[NIC-400 Interconnect] Remap mode

Hi everyone,

Currently. I have a concern about Remap mode when work with NIC-400 Interconnect.

As below snapshot:

http://infocenter.arm.com/help/topic/com.arm.doc.ddi0475g/DDI0475G_corelink_nic400_network_interconnect_r1p0_trm.pdf

(page 2-28)

(page 3-10)

My concern is: 
What is a tie-off port ? and how to configure it ?

Could you please help me ?

Thank you in advance.

Ho.