Raven Interrupt Controller

passed directly to processor 0. If the pass-through mode is disabled, the 8259 interrupts are delivered using the priority and distribution mechanisms of the RavenMPIC.

The RavenMPIC does not interact with the vector fetch from the 8259 interrupt controller.

Raven-Detected Errors

Raven-detected errors are grouped together and sent to the interrupt logic as a single interrupt source. The interrupt delivery mode for this interrupt is distributed. The Raven Error Vector Priority register should be programmed for high true level sensitive activation.

For system implementations where the RavenMPIC controller is not used, the Raven-Detected Error condition will be made available by a signal which is external to the Raven ASIC. Presumably this signal would be connected to an externally sourced interrupt input of a MPIC controller in a different device. Since the MPIC specification defines external I/O interrupts to operate in the distributed mode, the delivery mode of this error interrupt should be consistent.

Timers

There is a divide-by-eight prescaler which is synchronized to the Raven clock (MPC processor clock). The output of the prescaler enables the decrement of the four timers. The timers may be used for system timing or to generate periodic interrupts. Each timer has four registers which are used for configuration and control. They are:

1.Current Count register

2.Base Count register

3.Vector Priority register

4.Destination register

2

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Motorola MVME2300 Series manual Raven-Detected Errors, Timers