Nxp Semiconductors UM10237 用户手册

UM10237_2

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Remark: 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.

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.

Real time debugging.

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