Boundary scan questions

hi,

I am new to Boundary scan.

I am looking at some IO IP and the vendor has input ports called
CLOCKDR, UPDATEDR, SHIFTDR, MODE, and MODE1

I do not know what CLOCKDR, MODE and MODE1 are used for. I also don't
know where the signals come from in terms of the TAP controller.

Is CLOCKDR a logical AND of JTAG _TCK and SHIFTDR state?

Any help will be greatly appreciated.

huzaifa