Datasheet

SAM9G45 [DATASHEET]
Atmel-6438O-ATARM-SAM9G45-Datasheet_08-Dec-15
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8.4.6 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.
8.4.7 ARM9EJ-S Registers
The ARM9EJ-S core has a total of 37 registers.
 31 general-purpose 32-bit registers
 Six 32-bit status registers
Table 8-1 shows all the registers in all modes.