What is HardFault in arm?

A hard fault is an exception that occurs because of an error during normal or exception processing. As per the Cortex-M0 Devices Generic User Guide (revision r0p0), the following sources can cause a hard fault: execution of an SVC instruction at a priority equal or higher than SVCall.

What is HardFault handler?

The hardfault handler function provides the whole register set values when the hardfault was triggered. For example, the values of registers R0 to R3, R12, LR, PC, and xPSR are stored in memory position 0x07FC5600 . Use the Memory Browser tool (1) to view the contents stored in memory.

What are the different states of Cortex M0?

Arm® Cortex®-M0 in a nutshell

Armv6-M architecture.
Bus interface AHB-lite, Von Neumann bus architecture.
Thumb/Thumb-2 subset instruction support.
3-stages pipeline.
Non-maskable interrupt + 1 to 32 physical interrupts.
Wakeup interrupt controller.
Hardware single-cycle ((32×32) multiply.

How many cores does ARM Cortex M0 have?

32
The ARM Cortex-M is a group of 32-bit RISC ARM processor cores licensed by Arm Holdings.

What is HardFault in stm32?

Hard Fault: is caused by Bus Fault, Memory Management Fault, or Usage Fault if their handler cannot be executed. After reset, not all fault exceptions are enabled, and with every fault the Hard Fault execp- tion handler is executed.

What is link register in arm?

A link register is a special-purpose register which holds the address to return to when a function call completes. A link register is used in many instruction set architectures, such as PowerPC, ARM, and PA-RISC.

What does the link Register do?

A link register is a special-purpose register which holds the address to return to when a function call completes. This is more efficient than the more traditional scheme of storing return addresses on a call stack, sometimes called a machine stack.

What is Cortex-M0+?

The Arm® Cortex®-M0+ is the most energy-efficient Arm® processor available for embedded applications with design constraints. It features one of the smallest silicon footprint and minimal code size to allow developers to achieve 32-bit performance at 16 and 8-bit price points.

What is SVC in arm?

SVC – Service Call SVC is an exception mechanism provided by ARM Cortex-M processor core. Executing an SVC instruction generates a supervisor call, which is used to carry out privileged operations from within an OS Kernel. This allows application code to access and control the processor resources.

How and when is the link register used?

R14, link register (LR) R14 is also called the Link Register (LR). This is used for holding the return address when calling a function or subroutine. At the end of the function or subroutine, the program control can return to the calling program and resume by loading the value of LR into the Program Counter (PC).

How does the link register work?

Why am I hitting hard faults with my ARM Cortex-M0+?

If you’re hittingg hard faults with your ARM Cortex-M0+, it could be a problem with unaligned flash blocks. Eliminate your variables and narrow your scope when debugging. Join the DZone community and get the full member experience. To me, one of the most frustrating things working with ARM Cortex-M cores are the hard fault exceptions.

How does the ARM Cortex-M handle exception handling?

Each exception relates to an error condition. If the error occurs, the ARM Cortex-M core stops executing the current instruction, and branches to the exception’s handler function. This mechanism is just like that used for interrupts, where the ARM Cortex-M core branches to an interrupt handler when it accepts an interrupt.

What is the active stack pointer on ARM Cortex-M devices?

ARM Cortex-M devices have two stack pointers, msp & psp. Upon exception entry, the active stack pointer is encoded in bit 2 of the EXC_RETURN value pushed to the link register. If the bit is set, the psp was active prior to exception entry, else the msp was active.

What happens when you break in hardfault_handler with an exception?

Upon exception entry, the active stack pointer is encoded in bit 2 of the EXC_RETURN value pushed to the link register. If the bit is set, the psp was active prior to exception entry, else the msp was active. Let’s look at the state when we break in HardFault_Handler for a pathological example: