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Programmer’s Model
ARM DDI 0363E Copyright © 2009 ARM Limited. All rights reserved. 2-4
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2.3 Operating modes
In each state there are seven modes of operation:
• User (USR) mode is the usual mode for the execution of ARM or Thumb programs. It is
used for executing most application programs.
• Fast interrupt (FIQ) mode is entered on taking a fast interrupt.
• Interrupt (IRQ) mode is entered on taking a normal interrupt.
• Supervisor (SVC) mode is a protected mode for the operating system and is entered on
taking a Supervisor Call (SVC), formerly SWI.
• Abort (ABT) mode is entered after a data or instruction abort.
• System (SYS) mode is a privileged user mode for the operating system.
• Undefined (UND) mode is entered when an Undefined instruction exception occurs.
Modes other than User mode are collectively known as Privileged modes. Privileged modes are
used to service interrupts or exceptions, or access protected resources.