MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
25-24 Freescale Semiconductor
25.8 NPC Initialization/Application Information
25.8.1 Accessing NPC Tool-Mapped Registers
To initialize the TAP for NPC register accesses, the following sequence is required:
1. Enable the NPC TAP controller. This is achieved by asserting JCOMP and loading the
ACCESS_AUX_TAP_NPC instruction in the JTAGC.
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 5001-2003 standard for more detail.
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