You can connect the following debug registers between DBGTDI and DBGTDO:
Bypass Register
Device ID Code Register
Instruction Register
Scan Chain Select Register (SCREG)
Scan chain 0, Debug Id Register (DIDR)
Scan chain 1, Debug Status And Control Register (DSCR)
Scan chain 4, Instruction Transfer Register (ITR)
Scan chain 5.
Scan chain 6.
Scan chain 7.