MPC8280 datasheet(185/1386 Pages) FREESCALE

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System Interface Unit (SIU)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

4-13

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Spread. In the spread scheme, priorities are spread over the table so other sources can have lower

interrupt latencies. This scheme is also programmed in the SICR but cannot be changed

dynamically.

4.2.2.2

PIT, TMCNT, PCI, and IRQ Relative Priority

The MPC8280 has seven general-purpose interrupt requests (IRQs), five of which, with the PIT, the PCI

interrupt controller, and TMCNT, can be mapped to any XSIU location. IRQ6 and IRQ7 have fixed

priority.

4.2.2.3

Highest Priority Interrupt

In addition to the FCC/MCC/SCC relative priority option, SICR[HP] can be used to specify one interrupt

source as having highest priority. This interrupt remains within the same interrupt level as the other

interrupt controller interrupts, but is serviced before any other interrupt in the table.

If the highest priority feature is not used, select the interrupt request in XSIU1 to be the highest priority

interrupt; the standard interrupt priority order is used. SICR[HP] can be updated dynamically to allow the

user to change a normally low priority source into a high priority-source for a certain period.

4.2.3

Masking Interrupt Sources

By programming the SIU mask registers, SIMR_H and SIMR_L, the user can mask interrupt requests to

the core. Each SIMR bit corresponds to an interrupt source. To enable an interrupt, set the corresponding

SIMR bit. When a masked interrupt source has a pending interrupt request, the corresponding SIPNR bit

is set, even though the interrupt is not generated to the core. The user can mask all interrupt sources to

implement a polling interrupt servicing scheme.

When an interrupt source has multiple interrupting events, the user can individually mask these events by

programming a mask register within that block. Table 4-2 shows which interrupt sources have multiple

interrupting events. Figure 4-9 shows an example of how the masking occurs, using an SCC as an example.

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