Difference between interrupt & Exception

[v.s.n.kumar]

Hi,
Can anybody tell what is the difference between interrupt & Exceptions in embedded systems. I hear this the word exception in ARM. I know what is interrupt. but if both the words indicate the same meaning then why they are using the word Exception instead of interrupt in ARM-7.

 

[kripacharya]

I believe the word "exception" refers to an interruption of the normal flow of execution, but only due to some sort of error or problem. The signal itself could be in the form of an actual hardware interrupt, or it could be a 'soft' error.

An interrupt on the other hand is a hardware event which is usually a desired event signaling completion or detection of some condition external to the software flow. However if such a condition is considered an error, then that interrupt gets classified as an exception.

For example :
A clock generator's timer completion interrupt is usually a desired interrupt.
However the brown-out detect interrupt would be classified as an exception. Or a divide-by-zero interrupt would be an exception.

 

[v.s.n.kumar]

what is the difference between thumb instruction set & thumb-2 instruction set.

 

[Venkadesh_M]

ARM - 32 bit instruction set, high perform, low optimization
Thumb - 16 bit instruction set, low perform, high optimization
Thumb2 - mixture of ARM and Thumb which is only avail in ARM Cortex series

 

[embpic]

Thumb instructions are used to increase cpu throughput by executing two instrunction instead of one 32-bit.
Thumb execute 2 instruction in 1 machine cycle where as ARM execute 1.

 

[mdvrajkot]

Hello v.s.n.kumar ,

The basic difference between thumb and ARM is
1. Code Size (ARM having higher)
2. Thumb instructions - 16 bit & ARM instructions - 32 bit
3. Performance (Higher in ARM)

 

[ftsolutions]

In ARM processors, an exception causes different processor state switching and different register contents to be pushed on the processor stack than for a 'normal' interrupt.
The most common ARM processor exceptions include data abort exceptions, undefined instruction exceptions, and prefetch abort exceptions. With a 'normal' interrupt, some basic stack/register operations must be performed and the interrupt cleared in the VIC (Vectored Interrupt Controller) to resume normal operation. With a processor exception, there may not be a safe or easy way to attempt to resume where the processor had left off, and often one has to try to gracefully cleanup and prepare to reboot/restart the processor (get a "clean slate"). One method of doing this is to make the processor watchdog timer reset the processor.