PWM Generators

For ease of software, the LDFQx bits are buffered. When the LDFQx bits are changed, the reload frequency will not change until the previous reload cycle is completed. See Figure 12-6.

NOTE

When reading the LDFQx bits, the value is the buffered value (for example, not necessarily the value being acted upon).

RELOAD

RELOAD

 

 

RELOAD

 

RELOAD RELOAD RELOADRELOAD

 

CHANGE

 

RELOAD

 

 

 

 

CHANGE RELOAD

 

FREQUENCY TO

 

 

 

FREQUENCY TO

 

EVERY 4 CYCLES

 

EVERY CYCLE

Figure 12-6. Reload Frequency Change

PWMINT enables CPU interrupt requests as shown in Figure 12-7. When this bit is set, CPU interrupt requests are generated when the PWMF bit is set. When the PWMINT bit is clear, PWM interrupt requests are inhibited. PWM reloads will still occur at the reload rate, but no interrupt requests will be generated.

VDD

PWM RELOAD

RESET

D

LATCH

CK

PWMF

PWMINT

READ PWMF AS 1, WRITE PWMF AS 0 OR

RESET

CPU INTERRUPT REQUEST

Figure 12-7. PWM Interrupt Requests

To prevent a partial reload of PWM parameters from occurring while the software is still calculating them, an interlock bit controlled from software is provided. This bit informs the PWM module that all the PWM parameters have been calculated, and it is “okay” to use them. A new modulus, prescaler, and/or PWM value cannot be loaded into the PWM module until the LDOK bit in PWM control register 1 is set. When the LDOK bit is set, these new values are loaded into a second set of registers and used by the PWM generator at the beginning of the next PWM reload cycle as shown in Figure 12-8, Figure 12-9, Figure 12-10, and Figure 12-11. After these values are loaded, the LDOK bit is cleared.

NOTE

When the PWM module is enabled (via the PWMEN bit), a load will occur if the LDOK bit is set. Even if it is not set, an interrupt will occur if the PWMINT bit is set. To prevent this, the software should clear the PWMINT bit before enabling the PWM module.

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1

Freescale Semiconductor

123

Page 122 Page 124
Page 123
Image 123
Freescale Semiconductor MC68HC908MR16, MC68HC908MR32 manual Reload Frequency Change, PWM Interrupt Requests
Page 122 Page 124

MC68HC908MR16, MC68HC908MR32 specifications

Freescale Semiconductor's MC68HC908MR32 and MC68HC908MR16 microcontrollers are part of the popular HC08 family, designed primarily for embedded applications. These microcontrollers are particularly favored in automotive, industrial, and consumer product sectors due to their reliability and versatility.

One of the standout features of the MC68HC908MR series is its CMOS technology, which enhances performance while minimizing power consumption. This makes these microcontrollers suitable for battery-operated devices. They operate at a maximum clock frequency of 2 MHz and offer a 16-bit architecture, providing a solid balance between processing power and efficiency.

The MC68HC908MR32 variant is equipped with 32KB of flash memory, which allows for the storage of complex programs and extensive data handling. In contrast, the MC68HC908MR16 features 16KB of flash memory, making it ideal for simpler applications. Both microcontrollers also come with 1KB of RAM, enabling efficient data processing and real-time operations.

Another significant characteristic of these microcontrollers is their integrated peripherals. They come with multiple input/output (I/O) pins, which allow for connectivity with various sensors and actuators. The built-in timer systems offer precise timing control for automotive and industrial applications, while the Analog-to-Digital Converter (ADC) provides essential conversion capabilities for various analog signals.

For communication purposes, the MC68HC908MR series includes a serial communication interface, enabling easy integration with other devices and systems. This versatility facilitates the development of complex systems that require interaction with external components.

Security is another crucial aspect of these microcontrollers. They have built-in fail-safe mechanisms to ensure reliable operation under various conditions, making them suitable for critical systems. Additionally, their robust architecture helps to safeguard against potential disruptions or attacks.

In summary, Freescale Semiconductor's MC68HC908MR32 and MC68HC908MR16 microcontrollers are key players in the embedded systems landscape. Their blend of power efficiency, integrated features, and scalability ensures they remain relevant for a wide array of applications, making them a favored choice among engineers and developers looking for dependable solutions in a competitive market.
Top Page Image Contents