MC68HC908LD64 Datasheet, PDF (173/362 Pages) Freescale Semiconductor, Inc – Microcontrollers

Pulse Width Modulator (PWM)
PWM Registers
12.4 PWM Registers
The PWM module uses of nine registers for data and control functions.
• PWM data registers ($0070–$0077)
• PWM control register ($0078)
12.4.1 PWM Data Registers 0 to 7 (0PWM–7PWM)
Address: $0070–$0077
Bit 7
6
5
4
3
2
1
Bit 0
Read:
xPWM4 xPWM3 xPWM2 xPWM1
Write:
xPWM0
xBRM2
xBRM1
xBRM0
Reset: 0
0
0
0
0
0
0
0
Figure 12-2. PWM Data Registers 0 to 7 (0PWM–7PWM)
The output waveform of the eight 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 bus clock, the repetition rate of the output is hence f_OP ÷ 32.
Examples of PWM output waveforms are shown in Figure 12-4.
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 12-4.
MC68HC908LD64 — Rev. 3.0
Freescale Semiconductor
Pulse Width Modulator (PWM)
Data Sheet
173