LPC2131/2132/2138 User Manual - mct.net

Philips Semiconductors Preliminary User Manual
ARM-based Microcontroller
23. REALMONITOR
LPC2131/2132/2138
RealMonitor is a configurable software module which enables real time debug. RealMonitor is developed by ARM Inc. Information
presented in this chapter is taken from the ARM document RealMonitor Target Integration Guide (ARM DUI 0142A). It applies to
a specific configuration of RealMonitor software programmed in the on-chip ROM boot memory of this device.
Refer to the white paper "Real Time Debug for System-on-Chip" available at http://www.arm.com/support/
White_Papers?OpenDocument for background information.
FEATURES
Allows user to establish a debug session to a currently running system without halting or resetting the system.
Allows user time-critical interrupt code to continue executing while other user application code is being debugged.
APPLICATIONS
Real time debugging.
DESCRIPTION
RealMonitor is a lightweight debug monitor that allows interrupts to be serviced while user debug their foreground application. It
communicates with the host using the DCC (Debug Communications Channel), which is present in the EmbeddedICE logic.
RealMonitor provides advantages over the traditional methods for debugging applications in ARM systems. The traditional
methods include:
Angel (a target-based debug monitor).
Multi-ICE or other JTAG unit and EmbeddedICE logic (a hardware-based debug solution).
Although both of these methods provide robust debugging environments, neither is suitable as a lightweight real-time monitor.
Angel is designed to load and debug independent applications that can run in a variety of modes, and communicate with the
debug host using a variety of connections (such as a serial port or ethernet). Angel is required to save and restore full processor
context, and the occurrence of interrupts can be delayed as a result. Angel, as a fully functional target-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 is built into most ARM processors. To
perform debug tasks such as accessing memory or the processor registers, Multi-ICE must place the core into a debug state.
While the processor is in this state, which can be millions of cycles, normal program execution is suspended, and interrupts
cannot be serviced.
RealMonitor combines features and mechanisms from both Angel and Multi-ICE to provide the services and functions that are
required. In particular, it contains both the Multi-ICE communication mechanisms (the DCC using JTAG), and Angel-like support
for processor context saving and restoring. RealMonitor is pre-programmed in the on-chip ROM memory (boot sector). When
enabled It allows user to observe and debug while parts of application continue to run. Refer to section How to Enable
RealMonitor for details.
RealMonitor 253 November 22, 2004