
EM358x
22
Rev. 0.4
3.2 Event Manager
While the standard ARM
®
Cortex
TM
-M3 Nested Vectored Interrupt Controller provides top-level interrupts into the
CPU, the proprietary Event Manager provides second-level interrupts. The Event Manager takes a large variety of
hardware interrupt sources from the peripherals and merges them into a smaller group of interrupts in the NVIC.
Effectively, all second-level interrupts from a peripheral are “OR’d” together into a single interrupt in the NVIC. In
addition, the Event Manager provides missed indicators for the top-level peripheral interrupts with the register
INT_MISS.
The description of each peripheral’s interrupt configuration and flag registers can be found in the chapters of this
reference manual describing each peripheral. Figure 3-1 shows the Peripheral Interrupts Block Diagram.
Figure 3-1. Peripheral Interrupts Block Diagram
Given a peripheral, ‘periph’, the Event Manager registers (INT_periphCFG and INT_periphFLAG) follow the form:
INT_periphCFG enables and disables second-level interrupts. Writing 1 to a bit in the INT_periphCFG register
enables the second-level interrupt. Writing 0 to a bit in the INT_periphCFG register disables it. The
INT_periphCFG register behaves like a mask, and is responsible for allowing the INT_periphFLAG bits to
propagate into the top-level NVIC interrupts.
INT_periphFLAG indicates second-level interrupts that have occurred. Writing 1 to a bit in a INT_periphFLAG
register clears the second-level interrupt. Writing 0 to any bit in the INT_periphFLAG register is ineffective. The
INT_periphFLAG register is always active and may be set or cleared at any time, meaning if any second-level
interrupt occurs, then the corresponding bit in the INT_periphFLAG register is set regardless of the state of
INT_periphCFG.
If a bit in the INT_periphCFG register is set after the corresponding bit in the INT_periphFLAG register is set then
the second-level interrupt propagates into the top-level interrupts. The interrupt flags (signals) from the second-
level interrupts into the top-level interrupts are level-sensitive. If a top-level NVIC interrupt is driven by a second-
level EM interrupt, then the top-level NVIC interrupt cannot be cleared until all second-level EM interrupts are
cleared.
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