UM10139

Philips SemiconductorsVolume 1UM10139Chapter 24: RealMonitor24.4.5 Prefetch Abort modeRealMonitor uses four words on entry to its Prefetch abort interrupt handler.24.4.6 Data Abort modeRealMonitor uses four words on entry to its data abort interrupt handler.24.4.7 User/System modeRealMonitor makes no use of this stack.24.4.8 FIQ modeRealMonitor makes no use of this stack.24.4.9 Handling exceptionsThis section describes the importance of sharing exception handlers betweenRealMonitor and user application.24.4.10 RealMonitor exception handlingTo function properly, RealMonitor must be able to intercept certain interrupts andexceptions. Figure 72 illustrates how exceptions can be claimed by RealMonitor itself, orshared between RealMonitor and application. If user application requires the exceptionsharing, they must provide function (such as app_IRQDispatch ()). Depending on thenature of the exception, this handler can either:• Pass control to the RealMonitor processing routine, such as rm_irqhandler2().• Claim the exception for the application itself, such as app_IRQHandler ().In a simple case where an application has no exception handlers of its own, theapplication can install the RealMonitor low-level exception handlers directly into the vectortable of the processor. Although the IRQ handler must get the address of the VectoredInterrupt Controller. The easiest way to do this is to write a branch instruction ()into the vector table, where the target of the branch is the start address of the relevantRealMonitor exception handler.© Koninklijke Philips Electronics N.V. 2005. All rights reserved.User manual Rev. 01 — 15 August 2005 323