Datasheet

30
SAM9X35 [DATASHEET]
11055E–ATARM–10-Mar-2014
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 Interrupt Mode Fast Interrupt Mode
R0 R0 R0 R0 R0 R0
R1 R1 R1 R1 R1 R1
R2 R2 R2 R2 R2 R2
R3 R3 R3 R3 R3 R3
R4 R4 R4 R4 R4 R4
R5 R5 R5 R5 R5 R5
R6 R6 R6 R6 R6 R6
R7 R7 R7 R7 R7 R7
R8 R8 R8 R8 R8
R8_FIQ
R9 R9 R9 R9 R9
R9_FIQ
R10 R10 R10 R10 R10
R10_FIQ
R11 R11 R11 R11 R11
R11_FIQ
R12 R12 R12 R12 R12
R12_FIQ
R13 R13_SVC R13_ABORT R13_UNDEF R13_IRQ R13_FIQ
R14 R14_SVC R14_ABORT R14_UNDEF R14_IRQ R14_FIQ
PC PC PC PC PC PC
CPSR CPSR CPSR CPSR CPSR CPSR
SPSR_SVC
SPSR_ABO
RT
SPSR_UNDEF SPSR_IRQ SPSR_FIQ
Mode-specific banked registers