UM10139

Philips SemiconductorsVolume 1UM10139Chapter 24: RealMonitor– Undef exception caused by the undefined instructions in user foregroundapplication. This indicates an error in the application being debugged. RealMonitorstops the user application until a "Go" packet is received from the host.When one of these exceptions occur that is not handled by user application, the followinghappens:• RealMonitor enters a loop, polling the DCC. If the DCC read buffer is full, control ispassed to rm_ReceiveData() (RealMonitor internal function). If the DCC write buffer isfree, control is passed to rm_TransmitData() (RealMonitor internal function). If there isnothing else to do, the function returns to the caller. The ordering of the abovecomparisons gives reads from the DCC a higher priority than writes to thecommunications link.• RealMonitor stops the foreground application. Both IRQs and FIQs continue to beserviced if they were enabled by the application at the time the foreground applicationwas stopped.24.4 How to enable RealmonitorThe following steps must be performed to enable RealMonitor. A code example whichimplements all the steps can be found at the end of this section.24.4.1 Adding stacksUser must ensure that stacks are set up within application for each of the processormodes used by RealMonitor. For each mode, RealMonitor requires a fixed number ofwords of stack space. User must therefore allow sufficient stack space for bothRealMonitor and application.RealMonitor has the following stack requirements:Table 320: RealMonitor stack requirementProcessor ModeRealMonitor Stack Usage (Bytes)Undef 48Prefetch Abort 16Data Abort 16IRQ 824.4.2 IRQ modeA stack for this mode is always required. RealMonitor uses two words on entry to itsinterrupt handler. These are freed before nested interrupts are enabled.24.4.3 Undef modeA stack for this mode is always required. RealMonitor uses 12 words while processing anundefined instruction exception.24.4.4 SVC modeRealMonitor makes no use of this stack.© Koninklijke Philips Electronics N.V. 2005. All rights reserved.User manual Rev. 01 — 15 August 2005 322