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Chapter 36 Nexus Development Interface (NDI)
MPC5602P Microcontroller Reference Manual, Rev. 4
Freescale Semiconductor
907
output signal indicates that a debug session is in progress, and the OSR will indicate the CPU is in the
debug state. Instructions may the be single-stepped by scanning new values into the CPUSCR, and
performing a OnCE go+noexit command (See
Section 36.12.5.2, “e200z0h OnCE Command Register
). The CPU will then temporarily exit the debug state (but not the debug session) to execute the
instruction, and will then return to the debug state (again indicated via the OnCE Status Register (OSR)).
The debug session remains in force until the final OnCE go+exit command is executed, at which time the
CPU will return to the previous state it was in (unless a new debug request is pending). A scan into the
CPUSCR is required prior to executing each go+exit or go+noexit OnCE command.
36.12.2 JTAG/OnCE Pins
The JTAG/OnCE pin interface is used to transfer OnCE instructions and data to the OnCE control block.
Depending on the particular resource being accessed, the CPU may need to be placed in the Debug mode.
For resources outside of the CPU block and contained in the OnCE block, the processor is not disturbed,
and may continue execution. If a processor resource is required, an internal debug request (
dbg_dbgrq
)
may be asserted to the CPU by the OnCE controller, and causes the CPU to finish the current instruction
being executed, save the instruction pipeline information, enter Debug Mode, and wait for further
commands. Asserting
dbg_dbgrq
will cause the chip to exit the low power mode enabled by the setting
of MSR
WE
, as well as temporarily exiting the waiting, stopped or halted power management states.
details the primary JTAG/OnCE interface signals.
36.12.3 OnCE Internal Interface Signals
The following paragraphs describe the OnCE interface signals to other internal blocks associated with the
OnCE controller.
36.12.3.1 CPU Debug Request (dbg_dbgrq)
The
dbg_dbgrq
signal is asserted by the OnCE control logic to request the CPU to enter the debug state.
It may be asserted for a number of different conditions, and causes the CPU to finish the current instruction
being executed, save the instruction pipeline information, enter the debug mode, and wait for further
commands.
Table 36-9. JTAG/OnCE Primary Interface Signals
Signal Name
Type
Description
j_trst_b
I
JTAG test reset
j_tclk
I
JTAG test clock
j_tms
I
JTAG test mode select
j_tdi
I
JTAG test data input
j_tdo
O
Test data out to master controller or pad
j_tdo_en
1
1
j_tdo_en is asserted when the TAP controller is in the shift_DR or shift_IR state.
O
Enables TDO output buffer