MC68HC908MR8 Datasheet, PDF (161/372 Pages) Motorola, Inc – Microcontrollers

Pulse-Width Modulator for Motor Control (PWMMC)
Fault Protection
UP/DOWN COUNTER
MODULUS = 4
DEAD-TIME = 2
PWM VALUE = 3
OUTCTL
OUT1
OUT2
PWM1
PWM2
PWM1/PWM2
DEAD-TIME
2
2
2
2
DEAD-TIME INSERTED BECAUSE
WHEN OUTCTL WAS SET, THE
STATE OF OUT1 WAS SUCH THAT
PWM1 WAS DIRECTED TO TOGGLE
DEAD-TIMES INSERTED
BECAUSE OUT1 TOGGLES,
DIRECTING PWM1 TO
TOGGLE.
NO DEAD-TIME INSERTED
BECAUSE OUT1 IS NOT
TOGGLING.
Figure 9-20. Dead-Time Insertion During OUTCTL = 1
9.7 Fault Protection
Conditions may arise in the external drive circuitry which require that the
PWM signals become inactive immediately, such as an overcurrent fault
condition. Furthermore, it may be desirable to selectively disable
PWM(s) solely with software.
One or more PWM pins can be disabled (forced to their inactive state)
by applying a logic high to either of the two external fault pins or by
writing a logic high to either of the disable bits (DISX and DISY in PWM
control register 1). Figure 9-21 shows the structure of the PWM
disabling scheme. While the PWM pins are disabled, they are forced to
their inactive state. The PWM generator continues to run — only the
output pins are disabled
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor Pulse-Width Modulator for Motor Control (PWMMC)
Technical Data
161