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Exceptions and Exception Vectors
86
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
ARM Subsystem
2.4
Exceptions and Exception Vectors
Exceptions arise when the normal flow of the program must be temporarily halted. The exceptions that
occur in an ARM system are given below:
•
Reset exception: processor reset
•
FIQ interrupt: fast interrupt
•
IRQ interrupt: normal interrupt
•
Abort exception: abort indicates that the current memory access could not be completed. The abort
could be a pre-fetch abort or a data abort.
•
SWI interrupt: use software interrupt to enter supervisor mode.
•
Undefined exception: occurs when the processor executes an undefined instruction
The exceptions in the order of highest priority to lowest priority are: reset, data abort, FIQ, IRQ, pre-fetch
abort, undefined instruction, and SWI. SWI and undefined instruction have the same priority. The ARM is
configured with the VINITHI signal set high (VINITHI = 1), such that the vector table is located at address
FFFF 0000h. This address maps to the beginning of the ARM local RAM (8 KB).
NOTE:
The VINITHI signal is configurable by way of the register setting in CP15. However, it is not
recommended to set VINITHI = 0, as the device has no physical memory in the 0000 0000h
address region.
The default vector table is shown in
.
Table 2-1. Exception Vector Table for ARM
Vector Offset Address
Exception
Mode on entry
I Bit State on Entry
F Bit State on Entry
0h
Reset
Supervisor
Set
Set
4h
Undefined instruction
Undefined
Set
Unchanged
8h
Software interrupt
Supervisor
Set
Unchanged
Ch
Pre-fetch abort
Abort
Set
Unchanged
10h
Data abort
Abort
Set
Unchanged
14h
Reserved
—
—
—
18h
IRQ
IRQ
Set
Unchanged
1Ch
FIQ
FIQ
Set
Set