Advance Information MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
160 Pulse-Width Modulator for Motor Control (PWM MC) MOTOROLA
Pulse-Width Modulator for Motor Control
Figure 9-23. Dead-Time Insertion During OUTCTL = 1
9.7 Fault Protection
Conditions may arise in the external drive circuitry wh ich 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 any of the four external fault pins or by writing
a logic high to either of the disable bits (DISX and DISY in PWM control
register 1). Figure 9-25 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.
To allow for different motor configurations and the controlling of more
than one motor, the PWM disabling function is org anized a s two b anks,
bank X and bank Y. Bank information combines with information from
the disable mapping register to allow selective PWM disabling. Fault
UP/DOWN COUNTER
MODULUS = 4
DEAD-TIME = 2
OUTCTL
PWM1
PWM2
OUT1
OUT2
2
PWM1/PWM2 2 2
PWM VALUE = 3
DEAD-TIME INSERTED BECAUSE
WHEN OUTCTL WAS SET, THE
STATE OF OUT1 WAS SUCH THAT
PWM1 WAS DIRECTED TO TOGGLE
DEAD-TIME INSERTED
BECAUSE OUT1 TOGGLES,
DIRECTING PWM1 TO
TOGGLE
NO DEAD-TIME INSERTED
BECAUSE OUT1 IS NOT
TOGGLING
DEAD-TIME
2