Newer logic analyzers can download source files or symbol tables from the host to enable source-code debugging. You can single-step, set breakpoints, set, or read memory and registers over the serial link to an external debugger. You have visibility into the processor without all the external connections that other debugging techniques require. Another advantage of on-chip debugging is that little of the target hardware must be operational to start debugging. If you can power up the processor, the on-chip communications link will probably work.
Manufacturers refer to on-chip debugging by the type of interface.
IEEE 1149.1 defines the JTAG interface, which designers conceived as an access port for boundary-scan testing of complex ICs. Therefore, to make the most effective use of your time and budget, you should plan for debugging early in the project. Your input during the design phase may simplify debugging and even eliminate the need for expensive test equipment. In addition, you should be on the lookout for new debugging methods. You can bet that the debugging world will continue to change.