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S3C2410A PROGRAMMER'S MODEL
2-13
Software Interrupt
The software interrupt instruction (SWI) is used for entering Supervisor mode, usually to request a particular
supervisor function. A SWI handler should return by executing the following irrespective of the state (ARM or Thumb):
MOV PC,R14_svc
This restores the PC and CPSR, and returns to the instruction following the SWI.
NOTE
nFIQ, nIRQ, ISYNC, LOCK, BIGEND, and ABORT pins exist only in the ARM920T CPU core.
Undefined Instruction
When ARM920T comes across an instruction which it cannot handle, it takes the undefined instruction trap. This
mechanism may be used to extend either the THUMB or ARM instruction set by software emulation.
After emulating the failed instruction, the trap handler should execute the following irrespective of the state (ARM or
Thumb):
MOVS PC,R14_und
This restores the CPSR and returns to the instruction following the undefined instruction.
Exception Vectors
The following table shows the exception vector addresses.
Table 2-3. Exception Vectors
Address Exception Mode in Entry
0x00000000 Reset Supervisor
0x00000004 Undefined instruction Undefined
0x00000008 Software Interrupt Supervisor
0x0000000C Abort (prefetch) Abort
0x00000010 Abort (data) Abort
0x00000014 Reserved Reserved
0x00000018 IRQ IRQ
0x0000001C FIQ FIQ