Programmer’s Model
ARM DDI 0210C
Copyright © 2001, 2004 ARM Limited. All rights reserved.
2-7
2.5
Operating modes
The ARM7TDMI processor has seven modes of operation:
•
User mode is the usual ARM program execution state, and is used for executing
most application programs.
•
Fast Interrupt
(FIQ) mode supports a data transfer or channel process.
•
Interrupt
(IRQ) mode is used for general-purpose interrupt handling.
•
Supervisor mode is a protected mode for the operating system.
•
Abort mode is entered after a data or instruction Prefetch Abort.
•
System mode is a privileged user mode for the operating system.
Note
You can only enter System mode from another privileged mode by modifying the
mode bit of the
Current Program Status Register
(CPSR).
•
Undefined mode is entered when an undefined instruction is executed.
Modes other than User mode are collectively known as privileged modes. Privileged
modes are used to service interrupts or exceptions, or to access protected resources.
Each register has a mode identifier as listed in Table 2-1.
Table 2-1 Register mode identifiers
Mode
Mode identifier
User
usr
Fast interrupt
fiq
Interrupt
irq
Supervisor
svc
Abort
abt
System
sys
Undefined
und
Summary of Contents for ARM7TDMI
Page 6: ...Contents vi Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...
Page 10: ...List of Tables x Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...
Page 14: ...List of Figures xiv Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...
Page 46: ...Introduction 1 26 Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...
Page 120: ...Coprocessor Interface 4 18 Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...
Page 142: ...Debug Interface 5 22 Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...
Page 282: ...Glossary Glossary 6 Copyright 2001 2004 ARM Limited All rights reserved ARM DDI 0210C ...