RTEMS 4.6.99.3 On-Line Library

Board Support Packages Processor Initialization

RTEMS PowerPC Applications Supplement

6.3: Processor Initialization

It is the responsibility of the application's initialization code to initialize the CPU and board to a quiescent state before invoking the rtems_initialize_executive directive. It is recommended that the BSP utilize the predriver_hook to install default handlers for all exceptions. These default handlers may be overwritten as various device drivers and subsystems install their own exception handlers. Upon completion of RTEMS executive initialization, all interrupts are enabled.

If this PowerPC implementation supports on-chip caching and this is to be utilized, then it should be enabled during the reset application initialization code. On-chip caching has been observed to prevent some emulators from working properly, so it may be necessary to run with caching disabled to use these emulators.

In addition to the requirements described in the Board Support Packages chapter of the Applications User's Manual for the reset code which is executed before the call to rtems_initialize_executive, the PowrePC version has the following specific requirements:

Must leave the PR bit of the Machine State Register (MSR) set to 0 so the PowerPC remains in the supervisor state.
Must set stack pointer (sp or r1) such that a minimum stack size of MINIMUM_STACK_SIZE bytes is provided for the rtems_initialize_executive directive.
Must disable all external interrupts (i.e. clear the EI (EE) bit of the machine state register).
Must enable traps so window overflow and underflow conditions can be properly handled.
Must initialize the PowerPC's initial Exception Table with default handlers.

RTEMS PowerPC Applications Supplement