Software Implementation

– PWM clock frequency set to BUSCLK by prescaler bits PRSC0 and PRSC1

•DISMAP is a write-once register which controls the PWM pins to be disabled if an external fault occurs. When this register is written for the first time, it cannot be rewritten unless a reset occurs. PWM0 is not disabled when an external fault appears. PWM1 is disabled if an external fault appears.

•The FCR register controls the fault protection circuitry. A fault does not cause a CPU interrupt in hysteresis current control mode. The fault protection circuitry operates in automatic mode for DCM HW variation. In hysteresis current control mode operates in manual mode.

The PWM frequency is affected by the setup of the internal bus frequency, PWM modulus registers PMODH, PMODL, and the prescaler value in the PRSC0 and PRSC1 registers. Consequently, the PWM frequency is given by the equation:

PWM Frequency =

BusFrequency

[Hz; Hz, -, -]

(EQ 5-6)

PMOD-------------------------------------------------⋅ PRSC[0:1]

According to the setting, the PWM frequency is 40 kHz.

5.3.1.2 HRP Setup

The HRP provides two complementary outputs for controlling a half-bridge in a light ballast application. It uses a dithering control method to provide a high step resolution (< 4 ns) from an 8 MHz input clock when driving inductive loads.

For the to operate properly, the HRP registers must be set correctly. The HRP works in variable frequency mode with 50% duty cycle. The output frequency varies from 40 kHz up to 120 kHz, depending on the level of dimming required. The MCU BUSCLKX2 is 8 MHz. The transistors controlling the lamp require a deadtime of 1 µs. The deadtime must be set by software.

Four steps are required to configure the HRP:

1.Set the dithering timebase to the appropriate value

2.Set the deadtime to the appropriate value

3.Set HRPPERH:HRPPERL to select the desired frequency

4.Select variable frequency mode and enable the module

Detailed description follows:

1.Set the dithering timebase to appropriate value:

The dithering timebase is determined by HRPTBH:HRPTBL registers. It should be calculated according to the condition:

Dithering timebase (seconds) >= (1/max ballast frequency) HRPTBH:HRPTBL = (1/max ballast frequency) * BUSCLKX2

In this case, dithering timebase = 1/120 kHz = 8.33 µs For BUSCLKX2 = 8 Mhz, the HRPTBH:HRPTBL = $0054

2.Set deadtime to appropriate value:

The deadtime is defined by HRPDT register.

The transistors used in the ballast require 1 µs of deadtime to prevent both being on at the same time.

HRPDT register = required deadtime / (1 /BUSCLKX2)

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor

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Freescale Semiconductor M68HC08 manual PWM Frequency = BusFrequency Hz Hz
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M68HC08 specifications

Freescale Semiconductor, known for its innovative solutions in the field of embedded systems, developed the M68HC08 microcontroller family, which includes the MC68HC908QT2. This 8-bit microcontroller is engineered to meet the demands of diverse applications, including automotive, industrial, and consumer electronics.

The MC68HC908QT2 is designed around Freescale’s M68HC08 core, which is renowned for its efficient and reliable performance. This microcontroller integrates a powerful instruction set, enabling developers to create high-performance applications with relatively low power consumption. The device operates at a clock frequency of up to 3 MHz, which is adequate for various control tasks.

One of the key features of the MC68HC908QT2 is its memory architecture. It includes a 2 KB Flash memory for program storage, representing a significant advantage for developers requiring non-volatile memory. Additionally, it encompasses 128 bytes of EEPROM memory, allowing for data retention even after power loss. The microcontroller also has 256 bytes of RAM for efficient data manipulation during operation.

In terms of input/output capabilities, the MC68HC908QT2 supports a variety of interfacing options. The microcontroller features up to 20 general-purpose I/O pins for flexibility in connecting with peripheral devices. Additionally, it provides multiple analog-to-digital converters (ADC) and timers that facilitate efficient analog signal processing and precise control through timing functions.

The architecture of the MC68HC908QT2 also incorporates sophisticated on-chip peripherals, enhancing its functionality. These peripherals include PWM (Pulse Width Modulation) outputs, which are essential for applications requiring motor control and other precise duty cycle processes. The integrated watchdog timer ensures reliable operation by resetting the system in the event of an application failure.

Moreover, the MC68HC908QT2 is equipped with an efficient power management system, enabling operation in a low-power mode, ideal for battery-powered applications. This microcontroller is packaged in a compact 28-pin dual in-line package (DIP), making it suitable for space-constrained designs.

In summary, the Freescale Semiconductor MC68HC908QT2 microcontroller is distinguished by its robust performance, extensive memory options, and versatile I/O capabilities. Its advanced features, including built-in timers, ADC, and a power management system, make it an exceptional choice for developers seeking to implement reliable and efficient embedded solutions. With its comprehensive architecture, the MC68HC908QT2 remains a popular choice in the landscape of 8-bit microcontrollers.
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