SERIAL I/O PORT

Transmit

TXD

 

 

 

 

 

 

 

S3P1

S6P1

 

 

 

 

Write to

 

 

 

 

 

 

SBUF

 

 

 

 

 

 

S6P2

 

 

 

 

 

 

Shift

 

 

 

 

 

 

 

 

S6P2

 

S6P2

S6P2

S6P2

RXD

D0

D1

D2

D6

D7

S6P2

S6P2

 

 

 

 

 

TI

 

 

 

 

 

 

Receive

S1P1

 

TXD

S3P1 S6P1

Write to Set REN, Clear RI

SCON

S6P2

Shift

S6P2

S6P2

S6P2

S6P2

D0

D1

D6

D7

RXD

S6P2 S6P2

S5P2

RI

S1P1

A4124-02

Figure 10-3. Mode 0 Timing

10.2.1.2Reception (Mode 0)

To start a reception in mode 0, write to the SCON register. Clear bits SM0, SM1, and RI and set the REN bit.

Hardware executes the write to SCON in the last phase (S6P2) of a peripheral cycle (Figure 10-3). In the second peripheral cycle following the write to SCON, TXD goes low at S3P1 for the first clock-signal pulse, and the LSB (D0) is sampled on the RXD pin at S5P2. The D0 bit is then shift- ed into the shift register. After eight shifts at S6P2 of every peripheral cycle, the LSB (D7) is shift- ed into the shift register, and hardware asserts RI (S1P1) to indicate a completed reception. Software can then read the received byte from SBUF.

10-5

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Intel 8XC251SQ, 8XC251SA, 8XC251SP, 8XC251SB, Embedded Microcontroller manual Transmit, Receive
Page 176 Page 178

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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