8XC251SA, SB, SP, SQ USER’S MANUAL

The value in CCAPxL determines the duty cycle of the current period. The value in CCAPxH de- termines the duty cycle of the following period. Changing the value in CCAPxL over time mod- ulates the pulse width. As depicted in Figure 9-6, the 8-bit value in CCAPxL can vary from 0 (100% duty cycle) to 255 (0.4% duty cycle).

NOTE

To change the value in CCAPxL without glitches, write the new value to the high byte register (CCAPxH). This value is shifted by hardware into CCAPxL when CL rolls over from FFH to 00H.

The frequency of the PWM output equals the frequency of the PCA timer/counter input signal divided by 256. The highest frequency occurs when the FOSC/4 input is selected for the PCA tim- er/counter. For FOSC = 16 MHz, this is 15.6 KHz.

To program a compare/capture module for the PWM mode, set the ECOMx and PWMx bits in the module’s CCAPM x register. Table 9-3 lists the bit combinations for selecting module modes. Also select the desired input for the PCA timer/counter by programming the CPS0 and CPS1 bits in the CMOD register (see Figure 9-7). Enter an 8-bit value in CCAPxL to specify the duty cycle of the first period of the PWM output waveform. Enter an 8-bit value in CCAPxH to specify the duty cycle of the second period. Set the timer/counter run control bit (CR in the CCON register) to start the PCA timer/counter.

 

 

Duty

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CCAPxL

Cycle

 

 

 

 

Output Waveform

 

 

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

255

0.4%

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

230

10%

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

128

50%

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

25

90%

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

100%

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A4161-01

Figure 9-6. PWM Variable Duty Cycle

9-12

Page 165 Page 167
Page 166
Image 166
Intel 8XC251SP, 8XC251SA, 8XC251SQ, 8XC251SB, Embedded Microcontroller manual PWM Variable Duty Cycle
Page 165 Page 167

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.
Top Page Image Contents