8xC251Tx Hardware Description

3.2Special Function Register Definitions

The following describes the special function registers associated with the second serial I/O port and their bit definitions.

3.2.1SCON1

Address: 9AH

Reset Value: 0000 0000B

 

 

Table 6. SCON1 Special Function Register Definitions

 

 

 

 

 

 

 

 

 

Bit Number

Bit

 

 

 

 

Function

 

Mnemonic

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

7

FE1SM0

 

Framing Error Bit 1:

 

 

 

 

 

To Select this function, set the SMOD0 bit in the BGCON register. Set by hard-

 

 

 

ware to indicate an invalid stop bit. Cleared by software, not by valid frames

 

 

 

Second Serial I/O Port Mode Bit 0:

 

 

 

 

To select this function, clear the SMOD0 bit in the BGCON register. Software

 

 

 

writes to bit SM0 and SM1 to select the second serial I/O port operating

 

 

 

mode. Refer to SM1 bit for mode selections

 

 

 

 

 

 

6

SM1

 

Second Serial I/O Port Mode Bit 1:

 

 

 

 

Software write to bit SM0 and SM1 (above) to select the serial port operating

 

 

 

mode.

 

 

 

 

 

 

 

SM0

SM1

Mode

Description

Baud Rate

 

 

 

0

0

0

Shift Register

Fosc/12

 

 

 

0

1

1

8 bit UART

variable

 

 

 

1

0

2

9 bit UART

Fosc/32* or Fosc/64*

 

 

 

1

1

3

9 bit UART

variable

 

 

 

* Select by programming the SMOD0 bit in the BGCON register

 

 

 

 

 

5

SM2

 

Second Serial I/O Port Mode Bit 2:

 

 

 

 

Software writes to SM2 enable and disable the multiprocessor communica-

 

 

 

tion and automatic address recognition features. This allows the second

 

 

 

serial I/O port to differentiate between data and command frames and to rec-

 

 

 

ognize slave and broadcast addresses

 

 

 

 

 

 

 

4

REN1

 

Receive Enable Bit 1:

 

 

 

 

 

To enable reception, set this bit. To enable transmission, clear this bit

 

 

 

 

 

 

 

3

TB8

 

Transmit Bit 8:

 

 

 

 

 

 

In modes 2 and 3, software writes the ninth data bit to be transmitted to TB8.

 

 

 

Not used in modes 0 and 1

 

 

 

 

 

 

 

 

 

2

RB8

 

Receive Bit 8:

 

 

 

 

 

 

Mode 0: not used

 

 

 

 

 

 

Mode 1 (SM2 clear): Set or cleared by hardware to reflect the stop bit

 

 

 

received

 

 

 

 

 

 

Modes 2 and 3 (SM2 set): Set or cleared by hardware to reflect the ninth

 

 

 

data bit received

 

 

 

 

 

 

 

 

1

TI1

 

Second Serial I/O Port Transmit Interrupt Flag Bit:

 

 

 

 

Set by transmitter after the last data bit is transmitted. Cleared by software

 

 

 

 

 

0

RI1

 

Second Serial I/O Port Receive Interrupt Flag Bit:

 

 

 

 

Set by the receiver after the last data bit of a frame has been received.

 

 

 

Cleared by software

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

9

 

 

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Intel 8XC251SQ, 8xC251TB, 8XC251SA, 8XC251SP, 8xC251TQ, 8XC251SB specifications Bit Number Function Mnemonic
Page 14 Page 16

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.
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