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MC9328MX1 Reference Manual
MOTOROLA
Interrupt Controller (AITC)
10.5 ARM920T Processor Interrupt Controller Operation
This section discusses the ARM920T processor prioritization of various exceptions and interrupt sources,
two methods of enabling or disabling interrupts, and provides a typical pipeline sequence.
10.5.1 ARM920T Processor Prioritization of Exception Sources
The ARM920T processor prioritizes the various exceptions as follows:
•
Reset (highest priority)
•
Data Abort
•
Fast Interrupt
•
Normal Interrupt
•
Prefetch Abort
•
Undefined Instruction and SWI (lowest priority)
10.5.2 AITC Prioritization of Interrupt Sources
The AITC module prioritizes the various interrupt sources by source number. Higher source numbers have
higher priority. Fast interrupts always have higher priority than normal interrupts.
Interrupt requests are prioritized as follows:
1. Fast interrupt requests, in order of highest source number
2. Normal interrupt requests, in order of highest priority level, then in order of highest source
number with the same priority level
10.5.3 Assigning and Enabling Interrupt Sources
The interrupt controller provides flexible assignment of any interrupt source to either of the two ARM920T
processor interrupt request inputs. This is done by setting the appropriate bits in the INTENABLEH and
INTENABLEL registers and the INTTYPEH and INTTYPEL registers. Interrupt assignment is usually
done once during system initialization and does not affect interrupt latency.
Interrupt assignment is the first of three steps required to enable an interrupt source, and this is done by the
MC9328MX1 hardware. The second step is to program the source to generate interrupt requests. The final
step is to enable the interrupt inputs in the ARM920T processor by clearing the normal interrupt disable (I)
and/or the fast interrupt disable (F) bits in the processor status register (CPSR).
10.5.4 Enabling Interrupts Sources
There are two methods of enabling or disabling interrupts in the AITC. The first method is to directly read
the INTENABLEH and INTENABLEL registers, logically OR or BIT CLEAR these registers with a
generated mask, then write back to the INTENABLEH and INTENABLEL registers.
The second method is performing an atomic write to source number of the INTENNUM register. The
AITC decodes this 6-bit register and enables one of the 64 interrupt sources. The AITC automatically
generates a single hot enable mask and logically ORs this mask to the correct INTENABLEH and
INTENABLEL register. To disable interrupts, the procedure is exactly the same except the source number
is written to the INTDISNUM register.
Содержание DragonBall MC9328MX1
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Страница 86: ...2 18 MC9328MX1 Reference Manual MOTOROLA Signal Descriptions and Pin Assignments ...
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