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| Debugger General Information |
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| registers are invalidated. Input and output character queues are cleared. |
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| Onboard devices (timer, serial ports, etc.) are reset, and the first two serial |
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| ports are reconfigured to their default state. |
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| During WARM reset, the 166Bug variables and tables are preserved, as well as |
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| the target state registers and breakpoints. |
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Reset must be used if the processor ever halts, or if the 166Bug environment is ever lost (vector table is destroyed, stack corrupted, etc.).
Abort
Abort is invoked by pressing and releasing the ABORT switch on the MVME166 front panel. Whenever abort is invoked when executing a user program (running target code), a "snapshot" of the processor state is captured and stored in the target registers. For this reason, abort is most appropriate when terminating a user program that is being debugged. Abort should be used to regain control if the program gets caught in a loop, etc. The target PC, register contents, etc., help to pinpoint the malfunction.
Pressing and releasing the ABORT switch generates a local board condition which may interrupt the processor if enabled. The target registers, reflecting the machine state at the time the ABORT switch was pressed, are displayed on the screen. Any breakpoints installed in your code are removed and the breakpoint table remains intact. Control is returned to the debugger.
Break
A "Break" is generated by pressing and releasing the BREAK key on the terminal keyboard. Break does not generate an interrupt. The only time break is recognized is when characters are sent or received by the console port. Break removes any breakpoints in your code and keeps the breakpoint table intact. Break also takes a snapshot of the machine state if the function was entered using SYSCALL. This machine state is then accessible to you for diagnostic purposes.
Many times it may be desirable to terminate a debugger command prior to its completion; for example, during the display of a large block of memory. Break allows you to terminate the command.
SYSFAIL* Assertion/Negation
Upon a reset/powerup condition the debugger asserts the VMEbus SYSFAIL* line (refer to the VMEbus specification). SYSFAIL* stays asserted if any of the following has occurred:
MVME166 Single Board Computer Installation Guide |
