APPENDIX B

SIGNAL DESCRIPTIONS

This appendix provides reference information for the external signals of the 8XC251Sx. pin as- signments are shown in Figures B-1 (PLCC package) and B-2 (DIP package) and are listed by functional category in Table B-1.

Table B-2 describes each of the signals. It lists the signal type (input, output, power, or ground) and the alternative functions of multifunction pins. Table B-3 shows how configuration bits RD1:0 (referred to in Table B-2) configure the A17, A16. RD#, WR# and PSEN# pins for exter- nal memory accesses.

 

 

 

/ CEX1

/ CEX0

/ ECI

/ T2EX

/ T2

 

SS1

 

 

 

/ P0.0

/ P0.1

/ P0.2

/ P0.3

 

 

 

 

 

 

P1.4

P1.3

P1.2

P1.1

P1.0

 

 

CC

AD0

AD1

AD2

AD3

 

 

 

 

 

 

V

V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6 5

 

4 3 2 1

 

44 43 42 41 40

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

P1.5 / CEX2

 

7

 

 

 

 

 

 

 

 

8XC251SA

 

 

 

 

 

 

39

 

AD4 / P0.4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

P1.6 / CEX3 / WAIT#

 

8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

38

 

AD5 / P0.5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

P1.7 / CEX4 / A17 / WCLK

 

9

 

 

 

 

 

 

 

 

8XC251SB

 

 

 

 

 

 

37

 

AD6 / P0.6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RST

 

10

 

 

 

 

 

 

 

 

 

 

 

 

 

 

36

 

AD7 / P0.7

 

 

 

 

 

 

 

 

 

8XC251SP

 

 

 

 

 

 

 

P3.0 / RXD

 

11

 

 

 

 

 

 

 

 

 

 

 

 

 

 

35

 

EA# / VPP

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VCC2

 

12

 

 

 

 

 

 

 

8XC251SQ

 

 

 

 

 

 

34

 

VSS2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

P3.1 / TXD

 

13

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

33

 

ALE / PROG#

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

P3.2 / INT0#

 

14

 

View of component as

32

 

PSEN#

 

 

 

P3.3 / INT1#

 

15

 

31

 

A15 / P2.7

 

 

 

P3.4 / T0

 

16

 

mounted on PC board

30

 

A14 / P2.6

 

 

 

P3.5 / T1

 

17

18

 

19

 

20

 

21

 

22

 

23

 

24

 

25

 

26

 

27

 

28

 

29

 

A13 / P2.5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

/P3.6WR#

RD#// A16￿

XTAL2

XTAL1

V

V

/A8P2.0

/A9P2.1

/A10P2.2

/A11P2.3

/A12P2.4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SS

 

SS2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

P3.7

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A4205-02

Figure B-1. 8XC251SA, SB, SP, SQ 44-pin PLCC Package

B-1

Page 392 Page 394
Page 393
Image 393
Intel 8XC251SB, Embedded Microcontroller manual 8XC251SA, 8XC251SP, 8XC251SQ
Page 392 Page 394

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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