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Intel Embedded Microcontroller, 8XC251SA, 8XC251SP, 8XC251SQ Framing BIT Error Detection Modes 1, 2

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

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SERIAL I/O PORT

10.3 FRAMING BIT ERROR DETECTION (MODES 1, 2, AND 3)

Framing bit error detection is provided for the three asynchronous modes. To enable the framing bit error detection feature, set the SMOD0 bit in the PCON register (Figure 12-1 on page 12-2). When this feature is enabled, the receiver checks each incoming data frame for a valid stop bit. An invalid stop bit may result from noise on the serial lines or from simultaneous transmission by two CPUs. If a valid stop bit is not found, the software sets the FE bit in the SCON register (Figure 10-2).

Software may examine the FE bit after each reception to check for data errors. Once set, only soft- ware or a reset can clear the FE bit. Subsequently received frames with valid stop bits cannot clear the FE bit.

10.4 MULTIPROCESSOR COMMUNICATION (MODES 2 AND 3)

Modes 2 and 3 provide a ninth-bit mode to facilitate multiprocessor communication. To enable this feature, set the SM2 bit in the SCON register (Figure 10-2). When the multiprocessor com- munication feature is enabled, the serial port can differentiate between data frames (ninth bit clear) and address frames (ninth bit set). This allows the microcontroller to function as a slave processor in an environment where multiple slave processors share a single serial line.

When the multiprocessor communication feature is enabled, the receiver ignores frames with the ninth bit clear. The receiver examines frames with the ninth bit set for an address match. If the received address matches the slave’s address, the receiver hardware sets the RB8 bit and the RI bit in the SCON register, generating an interrupt.

NOTE

The ES bit must be set in the IE register to allow the RI bit to generate an interrupt. The IE register is described in Chapter 8, Interrupts.

The addressed slave’s software then clears the SM2 bit in the SCON register and prepares to re- ceive the data bytes. The other slaves are unaffected by these data bytes because they are waiting to respond to their own addresses.

10.5 AUTOMATIC ADDRESS RECOGNITION

The automatic address recognition feature is enabled when the multiprocessor communication feature is enabled (i.e., the SM2 bit is set in the SCON register).

10-7

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Intel Embedded Microcontroller, 8XC251SA manual Framing BIT Error Detection Modes 1, 2, Multiprocessor Communication Modes 2
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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.