Electrical Environment, Power and Ground Pins

8XC251SA, SB, SP, SQ USER’S MANUAL

11.2 ELECTRICAL ENVIRONMENT

The 8XC251Sx is a high-speed CHMOS device. To achieve satisfactory performance, its operat- ing environment should accommodate the device signal waveforms without introducing distor- tion or noise. Design considerations relating to device performance are discussed in this section. See the device data sheet for voltage and current requirements, operating frequency, and wave- form timing.

11.2.1 Power and Ground Pins

Power the 8XC251Sx from a well-regulated power supply designed for high-speed digital loads. Use short, low impedance connections to the power (VCC and VCC2) and ground (VSS, VSS1, and VSS2) pins.

VCC2 is a secondary power pin that reduces power supply noise. VSS1 and VSS2 are secondary ground pins that reduce ground bounce and improve power supply bypassing. The secondary power and ground pins are not substitutes for VCC and VSS. They are not required for proper de- vice operation; thus, the 8XC251Sx is compatible with designs that do not provide connections to these pins.

11.2.2 Unused Pins

To provide stable, predictable performance, connect unused input pins to VSS or VCC. Untermi- nated input pins can float to a mid-voltage level and draw excessive current. Unterminated inter- rupt inputs may generate spurious interrupts.

11.2.3 Noise Considerations

The fast rise and fall times of high-speed CHMOS logic may produce noise spikes on the power supply lines and signal outputs. To minimize noise and waveform distortion follow good board layout techniques. Use sufficient decoupling capacitors and transient absorbers to keep noise within acceptable limits. Connect 0.01 µF bypass capacitors between V CC and each VSS pin. Place the capacitors close to the device to minimize path lengths.

Multilayer printed circuit boards with separate VCC and ground planes help minimize noise. For additional information on noise reduction, see Application Note AP-125, “Designing Microcon- troller Systems for Electrically Noisy Environments.”

11-2

Embedded Microcontroller, 8XC251SP, 8XC251SA, 8XC251SQ, 8XC251SB specifications

The Intel 8XC251 series of embedded microcontrollers is a family of versatile and powerful devices, designed to meet the demands of a wide range of applications. With models such as the 8XC251SB, 8XC251SQ, 8XC251SA, and 8XC251SP, this series offers unique features while maintaining a high level of performance and reliability.

At the heart of the 8XC251 microcontrollers is the 8051 architecture, which provides a 16-bit processor capable of executing complex instructions efficiently. This architecture not only allows for a rich instruction set but also facilitates programming in assembly language and higher-level languages like C, which are essential for developing sophisticated embedded systems.

One of the significant features of the 8XC251 family is its integrated peripherals, including timer/counters, serial communication interfaces, and interrupt systems. These peripherals enable developers to implement timing functions, data communication, and real-time processing, all of which are crucial in modern embedded applications. The 8XC251SB and 8XC251SQ models, for instance, come equipped with multiple I/O ports that allow for interfacing with other devices and systems, enhancing their functionality in various environments.

The memory architecture of the 8XC251 devices is noteworthy, featuring on-chip ROM, RAM, and EEPROM. The on-chip memory allows for fast access times, which is essential for executing programs efficiently. Moreover, the EEPROM serves as non-volatile memory, enabling the storage of configuration settings and important data that must be retained even when power is lost.

In terms of operating voltage, the 8XC251 devices are designed to operate in a wide range, typically between 4.0V and 6.0V. This flexibility makes them suitable for battery-powered applications, where energy efficiency is critical. The power management features, including reduced power modes, further enhance their suitability for portable devices.

Lastly, the 8XC251 series is supported by a wide range of development tools and resources, allowing engineers and developers to streamline the development process. This support, combined with the microcontrollers' robust features, makes the Intel 8XC251 family a reliable choice for various embedded applications, such as industrial automation, automotive systems, and consumer electronics.

Overall, the Intel 8XC251SB, 8XC251SQ, 8XC251SA, and 8XC251SP deliver high performance, versatility, and ease of use, making them a preferred choice for embedded system designers looking to develop efficient and effective solutions.

Intel 8XC251SA Electrical Environment, Power and Ground Pins, Unused Pins, Noise Considerations

Models: Embedded Microcontroller 8XC251SP 8XC251SA 8XC251SQ 8XC251SB