MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
1381
Preliminary—Subject to Change Without Notice
system clock is locked, MDO[0] is negated and tools may begin Nexus configuration. Loss of lock
conditions that occur subsequent to the exit of power-on reset and the initial lock of the system clock do
not cause a Nexus reset, and therefore do not result in MDO[0] driven high.
32.6
Initialization/Application Information
32.6.1
Accessing NPC tool-mapped registers
To initialize the TAP for Nexus register accesses, the following sequence is required:
1. Enable the Nexus TAP controller
2. Load the TAP controller with the NEXUS-ENABLE instruction
To write control data to NPC tool-mapped registers, the following sequence is required:
1. Write the 7-bit register index and set the write bit to select the register with a pass through the
SELECT-DR-SCAN path in the TAP controller state machine.
2. Write the register value with a second pass through the SELECT-DR-SCAN path. Note that the
prior value of this register is shifted out during the write.
To read status and control data from NPC tool-mapped registers, the following sequence is required:
1. Write the 7-bit register index and clear the write bit to select register with a pass through
SELECT-DR-SCAN path in the TAP controller state machine.
2. Read the register value with a second pass through the SELECT-DR-SCAN path. Data shifted in
is ignored.
See the IEEE-ISTO 5001-2001 standard for more detail.