Creating A New Vector Table - Motorola MVME167 Series Installation Manual

Using the 167Bug Debugger
5

Creating a New Vector Table

5-16
The start address of this target vector table area is the base address
($00) of the debugger memory. This address is loaded into the
target-state VBR at powerup and cold-start reset and can be
observed by using the RD command to display the target-state
registers immediately after powerup.
The 167Bug initializes the target vector table with the debugger
vectors listed in Table 5-2 on page 5-13
locations with the address of a generalized exception handler (refer
to the 167Bug Generalized Exception Handler on page 5-17 in this
chapter). The target program may take over as many vectors as
desired by simply writing its own exception vectors into the table.
If the vector locations listed in
accompanying debugger functions are lost.
The 167Bug maintains a separate vector table for its own use. In
general, you do not have to be aware of the existence of the
debugger vector table. It is completely transparent and you should
never make any modifications to the vectors contained in it.
Your program may create a separate vector table in memory to
contain its exception vectors. If this is done, the program must
change the value of the VBR to point at the new vector table. In
order to use the debugger facilities you can copy the proper vectors
from the 167Bug vector table into the corresponding vector
locations in your program vector table.
The vector for the 167Bug generalized exception handler (described
in detail in 167Bug Generalized Exception Handler on page 5-17 in this
chapter) may be copied from offset $3C (uninitialized interrupt) in
the target vector table to all locations in your program vector table
where a separate exception handler is not used. This provides
diagnostic support in the event that your program is stopped by an
unexpected exception. The generalized exception handler gives a
formatted display of the target registers and identifies the type of
the exception.
and fills the other vector
Table 5-2 are overwritten then the