Motorola MVME166D2 用户手册

Using the 166Bug Debugger

4-10

If your application enables translation through the Memory Management 
Units (MMUs), and if your application utilizes resources of the debugger (e.g., 
system calls), your application must create the necessary translation tables for 
the debugger to have access to its various resources.  The debugger honors the 
enabling of the MMUs; it does not disable translation.  

As described in the Memory Requirements section in Chapter 3, 166Bug needs 
64KB of read/write memory to operate.  The 166Bug reserves a 1024-byte area 
for a user program vector table area and then allocates another 1024-byte area 
and builds an exception vector table for the debugger itself to use.  Next, 
166Bug reserves space for static variables and initializes these static variables 
to predefined default values.  After the static variables, 166Bug allocates space 
for the system stack, then initializes the system stack pointer to the top of this 
area.  

With the exception of the first 1024-byte vector table area, you must be 
extremely careful not to use the above-mentioned memory areas for other 
purposes.  You should refer to the Memory Requirements section in Chapter 3 to 
determine how to dictate the location of the reserved memory areas.  If, for 
example, your program inadvertently wrote over the static variable area 
containing the serial communication parameters, these parameters would be 
lost, resulting in a loss of communication with the system console terminal.  If 
your program corrupts the system stack, then an incorrect value may be 
loaded into the processor Program Counter (PC), causing a system crash.  

The only hardware resources used by the debugger are the EIA-232-D ports, 
which are initialized to interface to the debug terminal.  If these ports are 
reprogrammed, the terminal characteristics must be modified to suit, or the 
ports should be restored to the debugger-set characteristics prior to reinvoking 
the debugger.