ATmega328P datasheet(267/448 Pages) ATMEL

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267

8161D–AVR–10/09

ATmega48PA/88PA/168PA/328P

24. debugWIRE On-chip Debug System

24.1

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 Non-volatile Memories

24.2

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.

24.3

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 commu-

nication gateway between target and emulator.

Figure 24-1. The debugWIRE Setup

Figure 24-1 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.

GND

dW(RESET)

VCC

1.8 - 5.5V

ATmega328P Datasheet(PDF) 267 Page - ATMEL Corporation