Software Interrupt; Undefined Instruction; Exception Vectors - Samsung S3C2500B User Manual

PROGRAMMER' ' S MODEL

2.9.7 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
This restores the PC and CPSR, and returns to the instruction following the SWI.
nFIQ, nIRQ, ISYNC, LOCK, BIGEND, and ABORT pins exist only in the ARM9TDMI CPU core.

2.9.8 UNDEFINED INSTRUCTION

When ARM9TDMI 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
This restores the CPSR and returns to the instruction following the undefined instruction.

2.10 EXCEPTION VECTORS

The following table shows the exception vector addresses.
Address
0x00000000
0x00000004
0x00000008
0x0000000C
0x00000010
0x00000014
0x00000018
0x0000001C
2-14
PC,R14_svc
PC,R14_und
Table 2-3. Exception Vectors
Reset
Undefined instruction
Software Interrupt
Abort (prefetch)
Abort (data)
Reserved
IRQ
FIQ
NOTE
Exception Mode in Entry
Supervisor
Undefined
Supervisor
Abort
Abort
Reserved
IRQ
FIQ
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