8xC251Tx Hardware Description

1.0 INTRODUCTION TO THE 8xC251Tx

This Hardware Description describes the 8xC251TB, 8xC251TQ (referred to collectively as the 8xC251Tx) embedded microcontroller, which is the newest member of the MCS® 251 microcontroller family. The 8xC251Tx is pin and code compatible with the 8xC251Sx but is enhanced with the addition of new features.

This document addresses the differences between the two members of the MCS 251 microcontroller family. For a detailed description of the MCS 251 microcontroller core and standard peripherals shared by both the 8xC251Sx and 8xC251Tx, please refer to the 8xC251SA, 8xC251SB, 8xC251SP, 8xC251SQ Embedded Microcontroller User’s Manual (272795).

1.1Comparing the 8xC251Tx and 8xC251Sx

The differences between the 8xC251Tx and the 8xC251Sx are briefly described here.

The maximum operating frequency of the 8xC251Tx is 24 Mhz compared to 16 MHz for the 8xC251Sx.

The 8xC251Tx has two serial I/O ports while the 8xC251Sx has one. The pins for the second serial I/O port are multiplexed with other functional pins.

The 8xC251Tx has a new configuration option (Extended Data Float timing) to allow interfacing with slower memories. This feature is supported by a bit in the configuration byte, UCONFIG1. The corre- sponding bit in the 8xC251Sx has a different function.

The 8xC251Tx is offered in with factory programmed ROM while the 8xC251Sx is also offered with

OTPROM/EPROM.

P2 (A15-8)

P3

PSEN

P0 (A7- 0/D7-0)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PORT

 

 

EPROM/

 

RAM

 

 

 

 

 

 

0-3

 

 

ROM

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8

24

 

 

 

16

 

 

 

 

 

Memory Data

AddressData

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BusData

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Memory Address

 

 

16

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BUS INTERFACE UNIT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

16

 

24

 

INSTR

PC

 

 

Instruction

 

CPU

 

 

 

 

Sequencer

 

Interface

 

SRC1, SRC2

 

Memory

ALU

Register

Program

 

File

Counter

 

 

Data

 

DST

 

 

 

 

ALE

VCC

Peripheral Interface Unit

RESET

IB Bus

8

VSS

Clock and Reset Unit

Interrupt Handler Unit

Peripherals

3Timers

Serial I/O

WDT

PCA

2nd Serial I/O

XTAL2

XTAL1

P1

Figure 1. 8xC251Tx Block Diagram

1

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Intel 8XC251SA, 8xC251TB, 8XC251SP, 8XC251SQ, 8xC251TQ, 8XC251SB specifications Otprom/Eprom, XC251Tx Block Diagram

8XC251SP, 8XC251SA, 8XC251SQ, 8xC251TB, 8xC251TQ 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.