PXN20RM Datasheet, PDF (1174/1376 Pages) Freescale Semiconductor, Inc – PXN20 Microcontroller

Nexus Development Interface (NDI)
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.
36.6 e200z6 Class 3 Nexus Module (Nexus3+)
The Nexus3+ module provides real-time development capabilities for the device core in compliance with
the IEEE-ISTO Nexus 5001-2003 standard. This module provides development support capabilities
without requiring the use of address and data pins for internal visibility.
A portion of the pin interface (the JTAG port) is also shared with the OnCE / Nexus 1 unit. The
IEEE-ISTO 5001-2003 standard defines an extensible auxiliary port which is used in conjunction with
the JTAG port in e200z6 processors.
36.6.1 Nexus3+ Introduction
This section defines the auxiliary pin functions, transfer protocols and standard development features of
the Nexus3+ module. The development features supported are Program Trace, Data Trace, Watchpoint
Messaging, Ownership Trace, and Read/Write access via the JTAG interface. The Nexus3+ module also
supports two Class 4 features: Watchpoint Triggering and Processor Overrun Control.
NOTE
Throughout this section references are made to the auxiliary port and its
specific signals, such as MCKO, MSEO[1:0], MDO[11:0] and others. In
actual use, the device NPC module arbitrates the access of the single
auxiliary port. To simplify the description of the function of the Nexus3+
module, the interaction of the NPC is omitted and the behavior described as
if the module has its own dedicated auxiliary port.
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PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor