User guide

8 Debug Communications Channel

This chapter explains how to use of the Debug Communications Channel (DCC). It contains the following sections:

• About the Debug Communications Channel

• Command-line debugging commands

• Enabling comms channel viewing

• Target transfer of data

• Polled debug communications

• Interrupt-driven debug communications

• Access from Thumb state

• Semihosting.

8.1 About the Debug Communications Channel

The EmbeddedICE logic in ARM cores such as ARM7TDMI and ARM9TDMI contains a debug communications

channel. This enables data to be passed between the target and the host debugger using the JTAG port and a

protocol converter such as Multi-ICE, without stopping the program flow or entering debug state. This chapter

describes how the debug communications channel can be accessed by a program running on the target, and by the

host debugger.

ADS provides the following methods of accessing the debug communications channel:

• the armsd command-line debugger

• the Channel Viewer mechanism in AXD

• Multi-ICE semihosting.

Debug Communications Channel