Datasheet

29. debugWIRE On-chip Debug System

29.1 Features

• 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 Nonvolatile Memories

29.2 Overview

The debugWIRE on-chip debug system uses a wire with bi-directional interface to control the program

flow and execute AVR instructions in the CPU and to program the different nonvolatile memories.

29.3 Physical Interface

When the debugWIRE Enable (DWEN) bit is programmed to '0' and Lock bits are unprogrammed ('1'), 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 29-1. The debugWIRE Setup

GND

dW(RESET)

1.8 - 5.5V

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.

ATmega48PA/88PA/168PA

debugWIRE On-chip Debug System

Datasheet Complete

DS40002011A-page 334