ATmega640/1280/1281/2560/2561
A list of the On-chip Debug specific JTAG instructions is given in “On-chip Debug Spe-
cific JTAG Instructions” on page 299.
The JTAGEN Fuse must be programmed to enable the JTAG Test Access Port. In addi-
tion, the OCDEN Fuse must be programmed and no Lock bits must be set for the On-
chip debug system to work. As a security feature, the On-chip debug system is disabled
when either of the LB1 or LB2 Lock bits are set. Otherwise, the On-chip debug system
would have provided a back-door into a secured device.
The AVR Studio enables the user to fully control execution of programs on an AVR
device with On-chip Debug capability, AVR In-Circuit Emulator, or the built-in AVR
Instruction Set Simulator. AVR Studio® supports source level execution of Assembly
programs assembled with Atmel Corporation’s AVR Assembler and C programs com-
piled with third party vendors’ compilers.
AVR Studio runs under Microsoft® Windows® 95/98/2000 and Microsoft Windows NT®.
For a full description of the AVR Studio, please refer to the AVR Studio User Guide.
Only highlights are presented in this document.
All necessary execution commands are available in AVR Studio, both on source level
and on disassembly level. The user can execute the program, single step through the
code either by tracing into or stepping over functions, step out of functions, place the
cursor on a statement and execute until the statement is reached, stop the execution,
and reset the execution target. In addition, the user can have an unlimited number of
code Break Points (using the BREAK instruction) and up to two data memory Break
Points, alternatively combined as a mask (range) Break Point.
On-chip Debug Specific
JTAG Instructions
The On-chip debug support is considered being private JTAG instructions, and distrib-
uted within ATMEL and to selected third party vendors only. Instruction opcodes are
listed for reference.
PRIVATE0; 0x8
PRIVATE1; 0x9
PRIVATE2; 0xA
PRIVATE3; 0xB
Private JTAG instruction for accessing On-chip debug system.
Private JTAG instruction for accessing On-chip debug system.
Private JTAG instruction for accessing On-chip debug system.
Private JTAG instruction for accessing On-chip debug system.
299
2549A–AVR–03/05
ATMEL [ ATMEL ]
