UM10139

UM10139Chapter 24: RealMonitorRev. 01 — 15 August 2005User manualRealMonitor is a configurable software module which enables real time debug.RealMonitor is developed by ARM Inc. Information presented in this chapter is taken fromthe ARM document RealMonitor Target Integration Guide (ARM DUI 0142A). It applies toa specific configuration of RealMonitor software programmed in the on-chip ROM bootmemory of this device.Refer to the white paper "Real Time Debug for System-on-Chip" available athttp://www.arm.com/support/White_Papers?OpenDocument for background information.24.1 Features24.2 Applications24.3 Description• Allows user to establish a debug session to a currently running system without haltingor resetting the system.• Allows user time-critical interrupt code to continue executing while other userapplication code is being debugged.Real time debugging.RealMonitor is a lightweight debug monitor that allows interrupts to be serviced while userdebug their foreground application. It communicates with the host using the DCC (DebugCommunications Channel), which is present in the EmbeddedICE logic. RealMonitorprovides advantages over the traditional methods for debugging applications in ARMsystems. The traditional methods include:• Angel (a target-based debug monitor)• Multi-ICE or other JTAG unit and EmbeddedICE logic (a hardware-based debugsolution).Although both of these methods provide robust debugging environments, neither issuitable as a lightweight real-time monitor.Angel is designed to load and debug independent applications that can run in a variety ofmodes, and communicate with the debug host using a variety of connections (such as aserial port or ethernet). Angel is required to save and restore full processor context, andthe occurrence of interrupts can be delayed as a result. Angel, as a fully functionaltarget-based debugger, is therefore too heavyweight to perform as a real-time monitor.Multi-ICE is a hardware debug solution that operates using the EmbeddedICE unit that isbuilt into most ARM processors. To perform debug tasks such as accessing memory orthe processor registers, Multi-ICE must place the core into a debug state. While theprocessor is in this state, which can be millions of cycles, normal program execution issuspended, and interrupts cannot be serviced.© Koninklijke Philips Electronics N.V. 2005. All rights reserved.User manual Rev. 01 — 15 August 2005 319