Manuals / Intel / Computer Equipment / Computer Hardware

Intel 8XC251SB, 8XC251SA, 8XC251SP, 8XC251SQ manual Baud Rate Generator Mode, Clock-out Mode

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

1 458
Download 458 pages 25.38 Kb
Page 148
Image 148

8XC251SA, SB, SP, SQ USER’S MANUAL

8.6.3Baud Rate Generator Mode

This mode configures timer 2 as a baud rate generator for use with the serial port. Select this mode by setting the RCLK and/or TCLK bits in T2CON. See Table 8-3. For details regarding this mode of operation, refer to section 10.6, “Baud Rates.”

8.6.4Clock-out Mode

In the clock-out mode, timer 2 functions as a 50%-duty-cycle, variable-frequency clock (Figure 8-10). The input clock increments TL0 at frequency FOSC/2. The timer repeatedly counts to over- flow from a preloaded value. At overflow, the contents of the RCAP2H and RCAP2L registers are loaded into TH2/TL2. In this mode, timer 2 overflows do not generate interrupts. The formula gives the clock-out frequency as a function of the system oscillator frequency and the value in the RCAP2H and RCAP2L registers:

FOSC

Clock-out Frequency = --------------------------------------------------------------------------------------

4 × (65536 - RCAP2H, RCAP2L)

For a 16 MHz system clock, timer 2 has a programmable frequency range of 61 Hz to 4 MHz. The generated clock signal is brought out to the T2 pin.

Timer 2 is programmed for the clock-out mode as follows:

1.Set the T2OE bit in T2MOD. This gates the timer register overflow to the ÷2 counter.

2.Clear the C/T2# bit in T2CON to select FOSC/2 as the timer input signal. This also gates the output of the ÷2 counter to pin T2.

3.Determine the 16-bit reload value from the formula and enter in the RCAP2H/RCAP2L registers.

4.Enter a 16-bit initial value in timer register TH2/TL2. This can be the same as the reload value, or different, depending on the application.

5.To start the timer, set the TR2 run control bit in T2CON.

Operation is similar to timer 2 operation as a baud rate generator. It is possible to use timer 2 as a baud rate generator and a clock generator simultaneously. For this configuration, the baud rates and clock frequencies are not independent since both functions use the values in the RCAP2H and RCAP2L registers.

8-14

Page 147 Page 149
Page 148
Image 148
Intel 8XC251SB, 8XC251SA, 8XC251SP, 8XC251SQ, Embedded Microcontroller manual Baud Rate Generator Mode, Clock-out Mode
Page 147 Page 149

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.