Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

data will be ignored if AVEC is asserted before or at the same time as the DSACKsignals. The vector number supplied in an autovector operation is derived from the interrupt level of the current interrupt. When AVEC is asserted instead of DSACKduring an interrupt acknowledge cycle, the MC68340 ignores the state of the data bus and internally generates the vector number (the sum of the interrupt level plus 24 ($18)).

AVEC is multiplexed with CS0. The FIRQ bit in the SIM40 module configuration register controls whether the AVEC/CS0 pin is used as an autovector input or as CS0 (refer to Section 4 System Integration Module for additional information). AVEC is only sampled during an interrupt acknowledge cycle. During all other cycles, AVEC is ignored. Additionally, AVEC can be internally generated for external devices by programming the autovector register. Seven distinct autovectors can be used, corresponding to the seven levels of interrupt available with signals IRQ7–IRQ1. Figure 3-16 shows the timing for an autovector operation.

3.4.4.3SPURIOUS INTERRUPT CYCLE. Requested interrupts, whether internal or external, are arbitrated internally. When no internal module (including the SIM40, which responds for external requests) responds during an interrupt acknowledge cycle by arbitrating for the interrupt acknowledge cycle internally, the spurious interrupt monitor generates an internal bus error signal to terminate the vector acquisition. The MC68340 automatically generates the spurious interrupt vector number (24) instead of the interrupt

vector number in this case. When an external device does not respond to an interrupt acknowledge cycle with AVEC or DSACK, a bus monitor must assert BERR, which results in the CPU32 taking the spurious interrupt vector. If HALT is also asserted, the MC68340 retries the interrupt acknowledge cycle instead of using the spurious interrupt vector.

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MC68340 specifications

The Motorola MC68340 is a highly integrated microprocessor that was introduced in the early 1990s. It belongs to the 68000 family of microprocessors and is designed to cater to the demands of embedded systems, particularly in telecommunications and networking applications. This chip represents a significant evolution in microprocessor technology by combining a microprocessor core with additional peripherals on a single chip, making it an attractive solution for engineers looking to design compact and efficient systems.

One of the key features of the MC68340 is its 32-bit architecture, which allows for significant processing power and data handling capabilities. This architecture enables the processor to handle larger data sizes and perform more complex calculations compared to its 16-bit predecessors. The MC68340 operates at clock speeds typically ranging from 16 MHz to 25 MHz. Its dual instruction pipeline enhances throughput, allowing for simultaneous instruction fetches and executions, which significantly boosts performance.

A notable characteristic of the MC68340 is the inclusion of integrated peripherals, which help reduce the overall component count in a system. Key integrated components include a memory management unit (MMU), a direct memory access (DMA) controller, and various communication interfaces such as serial ports. The memory management capabilities enhance the processor's ability to manage memory resources efficiently, enabling it to support multitasking environments commonly found in modern computing.

In terms of connectivity, the MC68340 features connections for both synchronous and asynchronous serial communication, making it well-suited for networking tasks. The processor supports a range of bus standards, including address and data buses, which facilitate seamless interaction with peripheral devices.

Another important aspect of the MC68340 is its flexibility. The processor supports multiple operating modes, including multiple CPU configurations and compatibility with the Motorola 68000 family, allowing for easier integration into existing systems.

Moreover, the MC68340 boasts low power consumption compared to many of its contemporaries, making it an excellent choice for battery-operated applications, enhancing its appeal in sectors like telecommunications, industrial control, and automotive systems. Its combination of performance, integration, versatility, and efficiency has secured the MC68340 a reputable position in the annals of embedded systems technology, proving to be a valuable asset for developers and engineers alike.