Loop Mode Instruction Execution | Motorola MC68340 manual

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Freescale Semiconductor, Inc.

CPU32 uses instruction restart, which requires that only a small portion of the internal machine state be saved. After correcting the page fault, the machine state is restored, and the instruction is refetched and restarted. This process is completely transparent to the application program.

	SEQUENCER
	CONTROL	INSTRUCTION
	UNIT	INSTRUCTION
	UNIT	PREFETCH
		PREFETCH
		AND
		DECODE
DATA BUS	16	BUS	BUS CONTROL
	EXECUTION	BUS
		CONTROL

	UNIT
ADDRESS	UNIT
ADDRESS	32
BUS	32
BUS
	Figure 5-1. CPU32 Block Diagram

5.1.3 Loop Mode Instruction Execution

The CPU32 has several features that provide efficient execution of program loops. One of these features is the DBcc looping primitive instruction. To increase the performance of the CPU32, a loop mode has been added to the processor. The loop mode is used by any single-word instruction that does not change the program flow. Loop mode is implemented in conjunction with the DBcc instruction. Figure 5-2 shows the required form of an instruction loop for the processor to enter loop mode.

ONE-WORD INSTRUCTION

DBcc

DBcc DISPLACEMENT

$FFFC = 4

Figure 5-2. Loop Mode Instruction Sequence

The loop mode is entered when the DBcc instruction is executed and the loop displacement is –4. Once in loop mode, the processor performs only the data cycles associated with the instruction and suppresses all instruction fetches. The termination

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MC68340 USER’S MANUAL

5- 3

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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.

Motorola MC68340 manual Loop Mode Instruction Execution, CPU32 Block Diagram

Models: MC68340

Freescale Semiconductor, Inc...

Freescale Semiconductor, Inc.

Figure 5-1. CPU32 Block Diagram

5.1.3 Loop Mode Instruction Execution

Figure 5-2. Loop Mode Instruction Sequence

MC68340 specifications