Advance Information MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
136 Pulse-Width Modulator for Motor Control (PWM MC) MOTOROLA
Pulse-Width Modulator for Motor Control
9.10.4 PWM Control Register 1. . . . . . . . . . . . . . . . . . . . . . . . . . .171
9.10.5 PWM Control Register 2. . . . . . . . . . . . . . . . . . . . . . . . . . .173
9.10.6 Dead-Time Write-Once Register . . . . . . . . . . . . . . . . . . . .176
9.10.7 PWM Disable Mapping Write-Once Register. . . . . . . . . . . 176
9.10.8 Fault Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . .177
9.10.9 Fault Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179
9.10.10 Fault Acknowledge Register. . . . . . . . . . . . . . . . . . . . . . . .180
9.10.11 PWM Output Control Register . . . . . . . . . . . . . . . . . . . . . .182
9.11 PWM Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183
9.2 Introduction
This section describes the pulse-width modulator for motor control
(PWMMC, version A). The MC68HC908MR24 PWM module can
generate three complementary PWM pairs or six independent PWM
signals. These PWM signals can be center-aligned or edge-aligned. A
block diagram of the PWM module is shown in Figure 9-1.
A12-bit timer PWM counter is common to all six channels. PWM
resolution is one clock period for edge-aligned operation and two clock
periods for center-aligned operation. The clock period is dependent on
the internal operating frequency (fOP) and a programmable prescaler.
The highest resolution for edge-aligned operation is 125 ns
(fOP = 8 MHz). The highest resolution for center-aligned operation is
250 ns (fOP = 8 MHz).
When generating complementary PWM sign als, the module features
automatic dead-time insertion to the PWM output pairs and tran sparent
toggling of PWM data based upon sensed motor phase current polarity.
A summary of the PWM registers is shown in Figure 9-2.