Atmel Atmel-ICE User Manual

Accessing 16-bit registers
The Atmel AVR peripherals typically contain several 16-bit registers that can be accessed via the 8-bit
data bus (e.g.: TCNTn of a 16-bit timer). The 16-bit register must be byte accessed using two read or
write operations. Breaking in the middle of a 16-bit access or single stepping through this situation may
result in erroneous values.
Restricted I/O register access
Certain registers cannot be read without affecting their contents. Such registers include those which
contain flags which are cleared by reading, or buffered data registers (e.g.: UDR). The software front-end
will prevent reading these registers when in stopped mode to preserve the intended non-intrusive nature
of OCD debugging. In addition, some registers cannot safely be written without side-effects occurring -
these registers are read-only. For example:
• Flag registers, where a flag is cleared by writing '1' to any bit. These registers are read-only.
• UDR and SPDR registers cannot be read without affecting the state of the module. These registers
are not accessible.
4.4.12. megaAVR Special Considerations
Software breakpoints
Since it contains an early version of the OCD module, ATmega128[A] does not support the use of the
BREAK instruction for software breakpoints.
JTAG clock
The target clock frequency must be accurately specified in the software front-end before starting a debug
session. For synchronization reasons, the JTAG TCK signal must be less than one fourth of the target
clock frequency for reliable debugging. When programming via the JTAG interface, the TCK frequency is
limited by the maximum frequency rating of the target device, and not the actual clock frequency being
used.
When using the internal RC oscillator, be aware that the frequency may vary from device to device and is
affected by temperature and V
CC
changes. Be conservative when specifying the target clock frequency.
JTAGEN and OCDEN fuses
The JTAG interface is enabled using the JTAGEN fuse, which is programmed by default. This allows
access to the JTAG programming interface. Through this mechanism, the OCDEN fuse can be
programmed (by default OCDEN is un-programmed). This allows access to the OCD in order to facilitate
debugging the device. The software front-end will always ensure that the OCDEN fuse is left un-
programmed when terminating a session, thereby restricting unnecessary power consumption by the
OCD module. If the JTAGEN fuse is unintentionally disabled, it can only be re-enabled using SPI or High
Voltage programming methods.
If the JTAGEN fuse is programmed, the JTAG interface can still be disabled in firmware by setting the
JTD bit. This will render code un-debuggable, and should not be done when attempting a debug session.
If such code is already executing on the Atmel AVR device when starting a debug session, the Atmel-ICE
will assert the RESET line while connecting. If this line is wired correctly, it will force the target AVR device
into reset, thereby allowing a JTAG connection.
If the JTAG interface is enabled, the JTAG pins cannot be used for alternative pin functions. They will
remain dedicated JTAG pins until either the JTAG interface is disabled by setting the JTD bit from the
program code, or by clearing the JTAGEN fuse through a programming interface.
Atmel Atmel-ICE [USER GUIDE]
Atmel-42330C-Atmel-ICE_User Guide-10/2016
44

Atmel Atmel-ICE Specifications

General

Brand	Atmel
Model	Atmel-ICE
Category	Microcontrollers
Language	English

Summary

Introduction to Atmel-ICE Features

Atmel-ICE Features Overview

Describes the key features of the Atmel-ICE development tool, including compatibility and supported interfaces.

Getting Started with Atmel-ICE

Atmel-ICE Full Kit Contents

Lists the items included in the Atmel-ICE full kit, essential for initial setup and operation.

Assembling the Atmel-ICE Unit

Provides instructions on how to connect cables and prepare the Atmel-ICE unit for use.

Connecting the Atmel-ICE to Target Devices

Connecting AVR and SAM Target Devices

Explains how to connect the Atmel-ICE to various target microcontroller devices.

Connecting to a JTAG Target

Details the procedure for connecting the Atmel-ICE to target devices using the JTAG interface.

On-chip Debugging Introduction

Introduction to On-chip Debugging

Introduces the concept of on-chip debugging and its role in development.

Atmel-ICE Software Integration

Atmel Studio Integration

Explains how to integrate and use the Atmel-ICE with the Atmel Studio IDE.

Advanced Debugging Techniques

debugWIRE Target Techniques

Covers specific techniques and considerations for debugging with the debugWIRE interface.

Release History and Known Issues

Firmware Release History

Lists past firmware versions and their associated changes and improvements.

Product Compliance Overview

Information regarding the product's compliance with RoHS, WEEE, CE, and FCC regulations.

Introduction to System Requirements

System Requirements for Atmel-ICE

Outlines the necessary software and hardware requirements for using the Atmel-ICE.

Getting Started with Atmel-ICE Kits

Atmel-ICE Kit Overview

Provides a diagrammatic overview of the different Atmel-ICE kit options and their components.

Opening the Atmel-ICE Unit

Details the procedure for safely opening the Atmel-ICE unit.

Connecting Atmel-ICE to Targets

Connecting AVR and SAM Target Devices

Explains how to connect the Atmel-ICE to various target microcontroller devices.

Connecting to a JTAG Target

Details the procedure for connecting the Atmel-ICE to target devices using the JTAG interface.

Connecting to an SWD Target

Explains how to connect the Atmel-ICE to target devices using the SWD interface.

On-chip Debugging for SAM Devices

Introduction to On-chip Debugging

Introduces the concept of on-chip debugging and its role in development.

SAM Devices with JTAG/SWD

Details on-chip debugging for SAM devices using JTAG and SWD interfaces.

ARM CoreSight Components Description

Describes the CoreSight components used in Atmel ARM Cortex-M microcontrollers.

AVR UC3 Debugging with JTAG/aWire

Atmel AVR UC3 On-chip Debug System

Explains the on-chip debug system for Atmel AVR UC3 microcontrollers.

JTAG Physical Interface for AVR UC3

Details the physical JTAG interface for AVR UC3 devices.

tinyAVR, megaAVR, XMEGA Device Interfaces

JTAG Physical Interface for AVR Devices

Describes the JTAG physical interface for tinyAVR, megaAVR, and XMEGA devices.

Connecting to a JTAG Target

Guides on connecting the Atmel-ICE to JTAG targets for these device families.

Connecting to an SPI Target

Explains how to connect the Atmel-ICE to target devices using the SPI interface.

megaAVR Debugging Considerations

Software Breakpoints for megaAVR

Discusses limitations and usage of software breakpoints for megaAVR devices.

JTAG Clock Frequency for megaAVR

Details clock frequency considerations for JTAG debugging of megaAVR devices.

AVR XMEGA Debugging Considerations

OCD and Clocking for XMEGA

Explains OCD clocking behavior for XMEGA devices during stopped mode.

Hardware Breakpoints for XMEGA

Details the hardware breakpoint capabilities and restrictions for XMEGA devices.

debugWIRE Special Considerations

debugWIRE Enable Fuse (DWEN) Management

Details the importance and usage of the DWEN fuse for enabling debugwire functionality.

Atmel-ICE Hardware Description

Atmel-ICE Architecture Overview

Provides a block diagram and explanation of the Atmel-ICE's internal architecture.

Software Integration with Atmel Studio

Atmel Studio Integration Guide

Explains how to integrate and use the Atmel-ICE with the Atmel Studio IDE.

Programming Options Configuration

Details the configuration options for programming Atmel AVR and SAM devices.

Debug Options Configuration

Covers important configuration options for debugging within Atmel Studio.

Advanced Debugging Techniques

Atmel AVR UC3 Target Techniques

Discusses advanced debugging techniques applicable to Atmel AVR UC3 targets.

debugWIRE Target Techniques

Covers specific techniques and considerations for debugging with the debugwire interface.

Release History and Known Issues

Firmware Release History Details

Lists past firmware versions and their associated changes and improvements.

Known Issues with Atmel-ICE

Details known issues and limitations with the Atmel-ICE hardware and firmware.

Product Compliance Information

RoHS and WEEE Compliance

Information regarding the product's compliance with RoHS and WEEE directives.

CE and FCC Compliance

Details the product's compliance with CE and FCC regulations for electromagnetic emissions.

Revision History of Document