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Because I have not tested all electronic circuits mentioned on this pages, I cannot attest to their accuracy; therefore, I do not provide a warranty of any kind and cannot be held responsible in any manner.
The JTAG Debugger Based on ATmega644
15. June 2009 - 6:36 — admin
This JTAG Debugger from the Cornell university is based on an ATmega644 and it’s capable of controlling program execution by setting breakpoints and accessing registers and memory.
This project makes use of IEEE standard 1149.1, entitled Standard Test Access Port and Boundary-Scan Architecture. This standard was written by the Joint Test Action Group and is commonly referred to as JTAG. JTAG is commonly used to debug embedded systems and to program hardware devices.
This JTAG Debugger used two ATmega644 MCUs. You will program one of the microcontrollers with any arbitrary code, while the other microcontroller (the debugger) contains the actual debugging firmware.
Link: JTAG debugger