Topic       : Pure Assembler Documentation
Author      : John Kormylo
Version     : PASM.HYP 1.0
Subject     : Documentation/Pure Assembler
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Index Size  : 20262
HCP-Version : 3
Compiled on : Atari
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@lang       : en
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View Ref-File[ Vector Base Register ]

... points to a $400 byte area containing the exception vectors.
It is set to zero on a RESET interrupt, which is where the exception
vectors normally reside.

The VBR was intended for multi-tasking systems so that different
applications could use different exception vectors.

For example, debuggers usually insert their own exception vectors so
as to prevent hard crashes or to use Trace mode.  If some other
application crashes, you don't want your debugger suddenly popping up
with an error message.  Pure Debugger doesn't even allow accessories.

The VBR is set using the MOVEC instruction.

See also Exceptions.