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Exception Model
107
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Cortex
®
-M4F Processor
•
Usage Fault
A usage fault is an exception that occurs because of a fault related to instruction execution, such as:
–
An undefined instruction
–
An illegal unaligned access
–
Invalid state on instruction execution
–
An error on exception return
An unaligned address on a word or halfword memory access or division by zero can cause a usage
fault when the core is properly configured.
•
SVCall
A supervisor call (SVC) is an exception that is triggered by the SVC instruction. In an OS environment,
applications can use SVC instructions to access OS kernel functions and device drivers.
•
Debug Monitor
This exception is caused by the debug monitor (when not halting). This exception is active only when
enabled. This exception does not activate if it is a lower priority than the current activation.
•
PendSV
PendSV is a pendable, interrupt-driven request for system-level service. In an OS environment, use
PendSV for context switching when no other exception is active. PendSV is triggered using the
Interrupt Control and State (INTCTRL) register.
•
SysTick
A SysTick exception is an exception that the system timer generates when it reaches zero when it is
enabled to generate an interrupt. Software can also generate a SysTick exception using the Interrupt
Control and State (INTCTRL) register. In an OS environment, the processor can use this exception as
system tick.
•
Interrupt (IRQ)
An interrupt, or IRQ, is an exception signaled by a peripheral or generated by a software request and
fed through the NVIC (prioritized). All interrupts are asynchronous to instruction execution. In the
system, peripherals use interrupts to communicate with the processor.
For a list of the device-specific interrupts, see the data sheet.
For an asynchronous exception, other than reset, the processor can execute another instruction between
when the exception is triggered and when the processor enters the exception handler.
Privileged software can disable the exceptions that
shows as having configurable priority (see
the SYSHNDCTRL register in
and the DIS0 register in
).
For more information about hard faults, memory management faults, bus faults, and usage faults, see
.
(1)
0 is the default priority for all the programmable priorities.
(2)
See
(3)
See SYSPRI1 in
Table 1-19. Exception Types
Exception Type
Vector
Number
Priority
(1)
Vector Address or
Offset
(2)
Activation
–
0
–
0x0000.0000
Stack top is loaded from the first entry
of the vector table on reset.
Reset
1
–3 (highest)
0x0000.0004
Asynchronous
Nonmaskable Interrupt
(NMI)
2
–2
0x0000.0008
Asynchronous
Hard Fault
3
–1
0x0000.000C
Memory Management
4
Programmable
(3)
0x0000.0010
Synchronous
Bus Fault
5
Programmable
(3)
0x0000.0014
Synchronous when precise and
asynchronous when imprecise
Usage Fault
6
Programmable
(3)
0x0000.0018
Synchronous
–
7-10
–
–
Reserved