Abstract: This paper introduces a kind of method to achieve processor on-chip debugging and performance analysis by reusing JTAG interface.With SuperV DSP as the research prototype,in the scheme both debugger and performance analysis modules are designed and the corresponding instructions are extended to provide the following capabilities for on-chip debugging and performance analysis: run-control,breakpoint setting,the execution cycle numbers and cache missing rate counting.Software development and application optimization are greatly facilitated,with little effect on the processor performance and power consumption.