CHAPTER 2

ARCHITECTURAL OVERVIEW

The 8XC251Sx is the first member of the MCS® 251 microcontroller family. This family of 8-bit microcontrollers is a high-performance upgrade of the widely-used MCS 51® microcontrollers. It extends features and performance while maintaining binary-code compatibility and pin com- patibility with the 8XC51FX, so the impact on existing hardware and software is minimal. Typi- cal control applications for the 8XC251Sx include copiers, scanners, CD ROMs, and tape drives. It is also well suited for communications applications, such as phone terminals, business/feature phones, and phone switching and transmission systems.

This manual covers all memory options of the 8XC251SA, SB, SP, SQ and these options are listed in Table 2-1.

All MCS 251 microcontrollers share a set of common features:

•24-bit linear addressing and up to 16 Mbytes of memory

•a register-based CPU with registers accessible as bytes, words, and double words

•a page mode for accelerating external instruction fetches

•an instruction pipeline

•an enriched instruction set, including 16-bit arithmetic and logic instructions

•a 64-Kbyte extended stack space

•a minimum instruction-execution time of two clocks (vs. 12 clocks for MCS 51 microcon- trollers)

•three types of wait state solutions: real-time, RD#/WR#/PSEN#, and ALE

•binary-code compatibility with MCS 51 microcontrollers

Several benefits are derived from these features:

•preservation of code written for MCS 51 microcontrollers

•a significant increase in core execution speed in comparison with MCS 51 microcontrollers at the same clock rate

•support for larger programs and more data

•increased efficiency for code written in C

•dynamic bus control through real-time wait state operations

2-1

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Intel 8XC251SB, 8XC251SA, 8XC251SP, 8XC251SQ, Embedded Microcontroller manual Chapter Architectural Overview
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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.
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