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The following is an example of an exception handler which can pass an
exception along to the debugger:
*
***
EXCEPT - Exception handler
*
EXCEPT
SUBQ.L
LINK
MOVEM.L
:
: decide here if your code handles exception, if so, branch...
:
MOVE.L
MOVE.W
AND.W
MOVE.L
MOVEM.L
UNLK
RTS
162Bug Generalized Exception Handler
The 162Bug has a generalized exception handler which it uses to handle
all of the exceptions not listed in Table 4-2. For all these exceptions, the
target stack pointer is left pointing to the top of the exception stack frame
created. In this way, if an unexpected exception occurs during execution of
your code, you are presented with the exception stack frame to help
determine the cause of the exception. The following example illustrates
this:
Example: Bus error at address $F00000. It is assumed for this example that
an access of memory location $F00000 initiates bus error exception
processing.
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Preserving the Debugger Operating Environment
****
#4,A7
Save space in stack for a PC value.
A6,#0
Frame pointer for accessing PC space.
A0-A5/D0-D7,-(SP)
Save registers.
BUFVBR,A0
Pass exception to debugger; Get saved VBR.
14(A6),D0
Get the vector offset from stack frame.
#$0FFF,D0
Mask off the format information.
(A0,D0.W),4(A6)
Store address of debugger exc handler.
(SP)+,A0-A5/D0-D7
Restore registers.
A6
Put addr of exc handler into PC and go.
4
4-15
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