Sample Crystal Circuit | Motorola MC68340 guide

Freescale Semiconductor, Inc.

	330 k	4.7 pF
	330 k
	XTAL
MC68340	20 M	32.768 kHz
	20 M	32.768 kHz

EXTAL 10 pF

Figure 10-2. Sample Crystal Circuit

The circuit shown in Figure 10-3 is the typical circuit recommended by Statek Corporation, for 32768 kHz crystal, part number CX-IV. It is recommended to start with these values, but parameter values may need to be adjusted to compensate for variables in layout.

	470 k	10 pF
	470 k
	XTAL
MC68340	22 M	32.768 kHz
	22 M	32.768 kHz

EXTAL 20 pF

Figure 10-3. Statek Corporation Crystal Circuit

A separate power pin (VCCSYN ) is used to allow the clock circuits to operate with the rest of the device powered down and to provide increased noise immunity for the clock circuits.

The source for VCCSYN should be a quiet power supply, and external bypass capacitors (see Figure 10-4) should be placed as close as possible to the VCCSYN pin to ensure a stable operating frequency.

Additionally, the PLL requires that an external low-leakage filter capacitor, typically in the

range of 0.01 to 0.1 ∝F, be connected between the XFC and VCCSYN pins. The XFC capacitor should provide 50-MΩinsulation but should not be electrolytic. For external

clock mode without PLL, the XFC pin can be left open. Smaller values of the external filter capacitor provide a faster response time for the PLL, and larger values provide greater frequency stability. Figure 10-4 depicts examples of both an external filter capacitor and bypass capacitors for VCCSYN .

10-2MC68340 USER’S MANUALMOTOROLA

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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 Sample Crystal Circuit

Models: MC68340

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

Figure 10-2. Sample Crystal Circuit

Figure 10-3. Statek Corporation Crystal Circuit

MC68340 specifications