Datasheet

PIC32MX1XX/2XX
DS61168E-page 34 Preliminary  2011-2012 Microchip Technology Inc.
Coprocessor 0 also contains the logic for identifying
and managing exceptions. Exceptions can be caused
by a variety of sources, including alignment errors in
data, external events or program errors. Table 3-3 lists
the exception types in order of priority.
TABLE 3-3: MIPS32
®
M4K
®
PROCESSOR CORE EXCEPTION TYPES
3.3 Power Management
The MIPS
®
M4K
®
processor core offers a number of
power management features, including low-power
design, active power management and power-down
modes of operation. The core is a static design that
supports slowing or Halting the clocks, which reduces
system power consumption during Idle periods.
3.3.1 INSTRUCTION-CONTROLLED
POWER MANAGEMENT
The mechanism for invoking Power-Down mode is
through execution of the WAIT instruction. For more
information on power management, see Section 25.0
“Power-Saving Features”.
3.4 EJTAG Debug Support
The MIPS
®
M4K
®
processor core provides for an
Enhanced JTAG (EJTAG) interface for use in the soft-
ware debug of application and kernel code. In addition
to standard User mode and Kernel modes of operation,
the M4K
®
core provides a Debug mode that is entered
after a debug exception (derived from a hardware
breakpoint, single-step exception, etc.) is taken and
continues until a Debug Exception Return (DERET)
instruction is executed. During this time, the processor
executes the debug exception handler routine.
The EJTAG interface operates through the Test Access
Port (TAP), a serial communication port used for trans-
ferring test data in and out of the core. In addition to the
standard JTAG instructions, special instructions
defined in the EJTAG specification define which
registers are selected and how they are used.
Exception Description
Reset Assertion MCLR
or a Power-on Reset (POR).
DSS EJTAG debug single step.
DINT EJTAG debug interrupt. Caused by the assertion of the external EJ_DINT input or by setting the
EjtagBrk bit in the ECR register.
NMI Assertion of NMI signal.
Interrupt Assertion of unmasked hardware or software interrupt signal.
DIB EJTAG debug hardware instruction break matched.
AdEL Fetch address alignment error.
Fetch reference to protected address.
IBE Instruction fetch bus error.
DBp EJTAG breakpoint (execution of SDBBP instruction).
Sys Execution of SYSCALL instruction.
Bp Execution of BREAK instruction.
RI Execution of a reserved instruction.
CpU Execution of a coprocessor instruction for a coprocessor that is not enabled.
CEU Execution of a CorExtend instruction when CorExtend is not enabled.
Ov Execution of an arithmetic instruction that overflowed.
Tr Execution of a trap (when trap condition is true).
DDBL/DDBS EJTAG Data Address Break (address only) or EJTAG data value break on store (address + value).
AdEL Load address alignment error.
Load reference to protected address.
AdES Store address alignment error.
Store to protected address.
DBE Load or store bus error.
DDBL EJTAG data hardware breakpoint matched in load data compare.