EM346-RTR datasheet(99/142 Pages) SILABS

99 / 142 page

EM346

100

Rev 1.0

9. Interrupt System

The EM346's interrupt system is composed of two parts: a standard ARM® CortexTM-M3 Nested Vectored Interrupt

Controller (NVIC) that provides top-level interrupts, and a proprietary Event Manager (EM) that provides second-

level interrupts. The NVIC and EM provide a simple hierarchy. All second-level interrupts from the EM feed into top-

level interrupts in the NVIC. This two-level hierarchy allows for both fine granular control of interrupt sources and

coarse granular control over entire peripherals, while allowing peripherals to have their own interrupt vector.

"9.1. Nested Vectored Interrupt Controller (NVIC)" on page 100 provides a description of the NVIC and an overview

of the exception table (ARM nomenclature refers to interrupts as exceptions). "9.2. Event Manager" on page 102

provides a more detailed description of the Event Manager including a table of all top-level peripheral interrupts

and their second-level interrupt sources.

In practice, top-level peripheral interrupts are only used to enable or disable interrupts for an entire peripheral.

Second-level interrupts originate from hardware sources, and therefore are the main focus of applications using

interrupts.

9.1. Nested Vectored Interrupt Controller (NVIC)

The ARM® CortexTM-M3 Nested Vectored Interrupt Controller (NVIC) facilitates low-latency exception and interrupt

handling. The NVIC and the processor core interface are closely coupled, which enables low-latency interrupt

processing and efficient processing of late-arriving interrupts. The NVIC also maintains knowledge of the stacked

(nested) interrupts to enable tail-chaining of interrupts.

The ARM® CortexTM-M3 NVIC contains 10 standard interrupts that are related to chip and CPU operation and

management. In addition to the 10 standard interrupts, it contains 17 individually vectored peripheral interrupts

specific to the EM346.

The NVIC defines a list of exceptions. These exceptions include not only traditional peripheral interrupts, but also

more specialized events such as faults and CPU reset. In the ARM® CortexTM-M3 NVIC, a CPU reset event is

considered an exception of the highest priority, and the stack pointer is loaded from the first position in the NVIC

exception table. The NVIC exception table defines all exceptions and their position, including peripheral interrupts.

The position of each exception is important since it directly translates to the location of a 32-bit interrupt vector for

each interrupt, and defines the hardware priority of exceptions. Each exception in the table is a 32-bit address that

is loaded into the program counter when that exception occurs. Table 9.1 lists the entire exception table.

Exceptions 0 (stack pointer) through 15 (SysTick) are part of the standard ARM® CortexTM-M3 NVIC, while

exceptions 18 (Management) through 32 (Debug) are the peripheral interrupts specific to the EM346 peripherals.

The peripheral interrupts are listed in greater detail in Table 9.2.

EM346-RTR 数据表(PDF) 99 Page - Silicon Laboratories