Datasheet
The debugWIRE Setup shows the schematic of a target MCU, with debugWIRE enabled, and the
emulator connector. The system clock is not affected by debugWIRE and will always be the clock source
selected by the CKSEL Fuses.
When designing a system where debugWIRE will be used, the following observations must be made for
correct operation:
• Pull-up resistors on the dW/(RESET) line must not be smaller than 10kΩ. The pull-up resistor is not
required for debugWIRE functionality
• Connecting the RESET pin directly to V
CC
will not work.
• Capacitors connected to the RESET pin must be disconnected when using debugWire.
• All external reset sources must be disconnected.
26.4. Software Break Points
debugWIRE supports Break Points function in Program Memory by the AVR Break instruction. Setting a
break point in Atmel Studio will insert a BREAK instruction in the Program Memory. The Instruction
replaced by the BREAK instruction will be stored. When program execution is continued, the stored
instruction will be executed before continuing from the Program Memory. A break can be inserted
manually by putting the BREAK instruction in the program.
The Flash must be re-programmed each time when a Break Point is changed. This is automatically
handled by Atmel Studio through the debugWIRE interface. The use of Break Points will therefore reduce
the Flash Data retention. Devices used for debugging purposes should not be shipped to end customers.
26.5. Limitations of debugWIRE
The debugWIRE communication pin (dW) is physically located on the same pin as External Reset
(RESET). An External Reset source is therefore not supported when the debugWIRE is enabled.
A programmed DWEN Fuse enables some parts of the clock system to be running in all sleep modes.
This will increase the power consumption while in sleep. Thus, the DWEN Fuse should be disabled when
debugWire is not used.
26.6. Register Description
The following section describes the registers used with the debugWire.
Atmel ATmega16M1/32M1/64M1 [DATASHEET]
Atmel-8209F-ATmega16M1/32M1/64M1_Datasheet_Complete-10/2016
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