Method and apparatus for debugging a data processing system
View Patent ↗A data processing system ( 10 ) includes a CPU ( 12 ) and debug circuitry ( 16 ). CPU ( 12 ) can execute instructions which provide direct input to one or more of trigger circuitry ( 32 ), multi-function debug counters ( 34 ), combining logic ( 36 ), and action select and control logic ( 38 ). Breakpoints can be cascaded, and separate breakpoint sequences can be triggered from a same trigger. A selected trigger ( 117 ) can produce a resulting action or trigger ( 119 ) but only if it occurs in a predetermined order compared to one or more other triggers ( 117 ). Multi-function debug counters ( 34 ) can perform a wide variety of programmable functions, can be started and stopped using the same or separate triggers, and can be optionally concatenated with each other.
1. A data processing system, comprising:
a central processing unit coupled to a bus; and
a debug circuit comprising:
a first breakpoint unit, coupled to the bus, for detecting a breakpoint event and providing an initial trigger output and an action output in response to detecting the breakpoint event, wherein the initial action output identifies an initial action; and
a second breakpoint unit for receiving the initial trigger output and providing an output in response to the first trigger output; and
a first cascaded breakpoint unit for receiving the initial trigger output and providing a first cascaded trigger output in response to the initial trigger output.
2. The data processing system of claim 1 , wherein:
the debug circuit further comprises a second cascaded breakpoint unit for receiving the first cascaded trigger output and providing a final action output, wherein the final action output is for identifying a final action.
3. A data processing system, comprising:
a central processing unit coupled to a bus; and
a debug circuit, comprising:
a first breakpoint unit, coupled to the bus, for detecting a breakpoint event and providing a first output in response to detecting the breakpoint event; and
a first plurality of serially-connected breakpoint units for receiving the first output at a front end of the serially-connected breakpoints and providing a final output in response to the first output at a back end of the serially-connected breakpoints, wherein the final output is for identifying an action.
4. The data processing system of claim 3 , wherein the debug circuit further comprises a second breakpoint unit for receiving the first output and providing a second output responsive to the first output.
5. A debug circuit, comprising:
first breakpoint means for detecting a breakpoint event and providing a first output in response to detecting the breakpoint event, wherein the first output is a trigger;
second breakpoint means, coupled to the first breakpoint means, for providing a second output in response to the first output, wherein the second output is an action;
third breakpoint means, coupled to the first breakpoint means, for providing a third output in response to the first output; and
a fourth breakpoint means, coupled to the third breakpoint means, for providing a fourth output in response to the second output.
6. The debug circuit of claim 5 , wherein the fourth output is one of a trigger and an action.
7. The debug circuit of claim 5 , further comprising a counter coupled to the fourth output.
8. The debug circuit of claim 5 , wherein the first breakpoint means is further characterized as providing a first action output in response to detecting the breakpoint event.
9. The debug circuit of claim 5 , wherein the first output has a first portion coupled to the second breakpoint means and a second portion that identifies an action.
10. A method of debugging with respect to a breakpoint event, comprising:
detecting the breakpoint event;
generating a first action in response to the breakpoint event;
generating a second action in response to the breakpoint event; and
comparing results of the first action and the second action.
11. The method of claim 10 , wherein the step of generating the first action comprises:
generating a first trigger in response to detecting the breakpoint event; and
generating the first action in response to the first trigger.
12. The method of claim 11 , wherein the step of generating the second action comprises:
generating the second action in response to the first trigger.
13. The method of claim 11 , wherein the step of generating the second action comprises:
generating a second trigger in response to the first trigger; and
generating the second action in response to the second trigger.