NXP Semiconductors MPC5644A Reference Manual page 1686

Nexus Port Controller (NPC)
37.5.3.1 Enabling the NPC TAP controller
Assertion of the power-on reset signal or setting JCOMP to a value other than the NPC enable encoding
resets the NPC TAP controller. When not in power-on reset, the NPC TAP controller is enabled by driving
JCOMP with the NPC enable value and exiting the Test-Logic-Reset state. Loading the NEXUS-ENABLE
instruction then grants access to Nexus debug.
MPC5644A Microcontroller Reference Manual, Rev. 6
1686 Freescale Semiconductor