23. debugWIRE On-chip Debug System
23.1 Features
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Complete program flow control
Emulates all on-chip functions, both digital and analog, except RESET pin
Real-time operation
Symbolic debugging support (both at C and assembler source level, or for other HLLs)
Unlimited number of program break points (using software break points)
Non-intrusive operation
Electrical characteristics identical to real device
Automatic configuration system
High-speed operation
Programming of non-volatile memories
23.2 Overview
The debugWIRE on-chip debug system uses a one-wire, bi-directional interface to control the program flow, execute AVR®
instructions in the CPU and to program the different non-volatile memories.
23.3 Physical Interface
When the debugWIRE Enable (DWEN) Fuse is programmed and Lock bits are unprogrammed, the debugWIRE system
within the target device is activated. The RESET port pin is configured as a wire-AND (open-drain) bi-directional I/O pin with
pull-up enabled and becomes the communication gateway between target and emulator.
Figure 23-1. The debugWIRE Setup
1.8 - 5.5V
VCC
dw
dw(RESET)
GND
Figure 23-1 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:
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Pull-up resistors on the dW/(RESET) line must not be smaller than 10k. The pull-up resistor is not required for
debugWIRE functionality.
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Connecting the RESET pin directly to VCC will not work.
Capacitors connected to the RESET pin must be disconnected when using debugWire.
All external reset sources must be disconnected.
ATmega16/32/64/M1/C1 [DATASHEET]
239
7647O–AVR–01/15
MICROCHIP [ MICROCHIP ]
