AT91SAM View Datasheet(PDF) - Atmel Corporation
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MFG CO.
'AT91SAM' PDF : 1185 Pages View PDF
9.4.6
ARM9EJ-S Operating Modes
In all states, there are seven operation modes:
• User mode is the usual ARM program execution state. It is used for executing most application programs
• Fast Interrupt (FIQ) mode is used for handling fast interrupts. It is suitable for high-speed 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
• Undefined mode is entered when an undefined instruction exception occurs
Mode changes may be made under software control, or may be brought about by external interrupts or exception
processing. Most application programs execute in User Mode. The non-user modes, known as privileged modes,
are entered in order to service interrupts or exceptions or to access protected resources.
9.4.7
ARM9EJ-S Registers
The ARM9EJ-S core has a total of 37 registers.
• 31 general-purpose 32-bit registers
• 6 32-bit status registers
Table 9-1 shows all the registers in all modes.
Table 9-1. ARM9TDMI Modes and Registers Layout
User and
System Mode
Supervisor
Mode
Abort Mode
Undefined
Mode
R0
R0
R0
R0
R1
R1
R1
R1
R2
R2
R2
R2
R3
R3
R3
R3
R4
R4
R4
R4
R5
R5
R5
R5
R6
R6
R6
R6
R7
R7
R7
R7
R8
R8
R8
R8
R9
R9
R9
R9
R10
R10
R10
R10
R11
R11
R11
R11
R12
R12
R12
R12
R13
R13_SVC
R13_ABORT R13_UNDEF
R14
R14_SVC
R14_ABORT R14_UNDEF
PC
PC
PC
PC
Interrupt
Mode
R0
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
R13_IRQ
R14_IRQ
PC
Fast Interrupt
Mode
R0
R1
R2
R3
R4
R5
R6
R7
R8_FIQ
R9_FIQ
R10_FIQ
R11_FIQ
R12_FIQ
R13_FIQ
R14_FIQ
PC
CPSR
CPSR
CPSR
CPSR
CPSR
CPSR
SAM9G45 [DATASHEET] 35
6438K–ATARM–12-Feb-13
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