Exception Control

14.5 Exception Control

Normal, sequential program execution can be changed in three different ways:

1.Interrupts:

a.Maskable hardware CPU interrupts

b.Non-maskable software interrupt instruction (SWI)

2.Reset

3.Break interrupts

14.5.1 Interrupts

At the beginning of an interrupt, the CPU saves the CPU register contents on the stack and sets the interrupt mask (I bit) to prevent additional interrupts. At the end of an interrupt, the return-from-interrupt (RTI) instruction recovers the CPU register contents from the stack so that normal processing can resume. Figure 14-7shows interrupt entry timing. Figure 14-9shows interrupt recovery timing.

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INTERRUPT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I BIT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IAB

 

DUMMY

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SP – 1

 

SP – 2

 

 

SP – 3

SP – 4

VECT H

 

VECT L

 

 

START

 

 

 

 

 

 

 

 

 

 

 

 

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IDB

 

 

 

DUMMY

 

 

PC – 1[7:0] PC – 1[15:8]

X

 

 

A

 

 

CCR

 

 

 

 

V DATA H V DATA L OPCODE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R/W

Figure 14-7.Interrupt Entry

Interrupts are latched, and arbitration is performed in the SIM at the start of interrupt processing. The arbitration result is a constant that the CPU uses to determine which vector to fetch. Once an interrupt is latched by the SIM, no other interrupt can take precedence, regardless of priority, until the latched interrupt is serviced (or the I bit is cleared). See Figure 14-8.

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1

Freescale Semiconductor

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Freescale Semiconductor MC68HC908MR16, MC68HC908MR32 manual Exception Control, Interrupts
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MC68HC908MR16, MC68HC908MR32 specifications

Freescale Semiconductor's MC68HC908MR32 and MC68HC908MR16 microcontrollers are part of the popular HC08 family, designed primarily for embedded applications. These microcontrollers are particularly favored in automotive, industrial, and consumer product sectors due to their reliability and versatility.

One of the standout features of the MC68HC908MR series is its CMOS technology, which enhances performance while minimizing power consumption. This makes these microcontrollers suitable for battery-operated devices. They operate at a maximum clock frequency of 2 MHz and offer a 16-bit architecture, providing a solid balance between processing power and efficiency.

The MC68HC908MR32 variant is equipped with 32KB of flash memory, which allows for the storage of complex programs and extensive data handling. In contrast, the MC68HC908MR16 features 16KB of flash memory, making it ideal for simpler applications. Both microcontrollers also come with 1KB of RAM, enabling efficient data processing and real-time operations.

Another significant characteristic of these microcontrollers is their integrated peripherals. They come with multiple input/output (I/O) pins, which allow for connectivity with various sensors and actuators. The built-in timer systems offer precise timing control for automotive and industrial applications, while the Analog-to-Digital Converter (ADC) provides essential conversion capabilities for various analog signals.

For communication purposes, the MC68HC908MR series includes a serial communication interface, enabling easy integration with other devices and systems. This versatility facilitates the development of complex systems that require interaction with external components.

Security is another crucial aspect of these microcontrollers. They have built-in fail-safe mechanisms to ensure reliable operation under various conditions, making them suitable for critical systems. Additionally, their robust architecture helps to safeguard against potential disruptions or attacks.

In summary, Freescale Semiconductor's MC68HC908MR32 and MC68HC908MR16 microcontrollers are key players in the embedded systems landscape. Their blend of power efficiency, integrated features, and scalability ensures they remain relevant for a wide array of applications, making them a favored choice among engineers and developers looking for dependable solutions in a competitive market.
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