M68HC08 datasheet(150/288 Pages) FREESCALE

150 / 288 page

Pulse Width Modulator (PWM)

Data Sheet

MC68HC908BD48 — Rev. 2.1

150

Pulse Width Modulator (PWM)

Freescale Semiconductor

11.4.1 PWM Data Registers 0 to 15 (0PWM–15PWM)

The output waveform of the 16 PWM channels are each configured by

an 8-bit register, which contains a 5-bit PWM in MSB portion and a 3-bit

binary rate multiplier (BRM) in LSB portion

xPWM4–xPWM0 — PWM Bits

The value programmed in the 5-bit PWM portion will determine the pulse

length of the output. The clock to the 5-bit PWM portion is the system

clock (CPU clock), the repetition rate of the output is hence fOP ÷ 32.

Examples of PWM output waveforms are shown in Figure 11-3.

xBRM2–xBRM0 — Binary Rate Multiplier Bits

The 3-bit BRM will generate a number of narrow pulses which are

equally distributed among an 8-PWM-cycle frame. The number of pulses

generated is equal to the number programmed in the 3-bit BRM portion.

Examples of PWM output waveforms are shown in Figure 11-3.

Address:

$0020–$0027 and $0051–$0058

Bit 7

654321

Bit 0

Read:

xPWM4

xPWM3

xPWM2

xPWM1

xPWM0

xBRM2

xBRM1

xBRM0

Write:

Reset:

00000000

Figure 11-1. PWM Data Registers 0 to 15 (0PWM–15PWM)

M68HC08 Datasheet(PDF) 150 Page - Freescale Semiconductor, Inc