mc68hc908lb8 Freescale Semiconductor, Inc, mc68hc908lb8 Datasheet - Page 150

• Manufacturer Part Number: mc68hc908lb8
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Pulse Width Modulator with Fault Input (PWM)
mode) or with software (manual mode). The fault pin has an associated FMODE bit to control the PWM
re-enabling method. Automatic mode is selected by setting the FMODE bit in the fault control register.
Manual mode is selected when FMODE is clear.
The operation of the fault pin is asnynchronous. If it is enabled by either the MAP0 or MAP1 disable bits
and the fault pin goes high, the associated PWM(s) outputs are immediately disabled without waiting for
the next bus cycle.
The location of the fault pin is software configurable to one of two locations. Enabling the fault functionality
of a given pin does not disconnect that pin from any other module that is trying to use the pin.
15.5.1.1 Automatic Mode
In automatic mode, the PWM(s) are disabled immediately once a fault condition is detected (logic high).
The PWM(s) remain disabled until the fault condition is cleared (logic low) and a new PWM cycle begins
as shown in
The fault pin’s logic state is reflected in the FPIN bit. Any write to this bit is overwritten by the pin state.
The FFLAG event bit is set with each rising edge of the fault pin. To clear the FFLAG bit, the user must
write a 1 to the FTACK bit.
150
Note:
In manual mode (FMODE = 0), fault may be cleared only if a logic level low at the input of the fault pin is present.
FAULT
PIN1
LOGIC HIGH FOR FAULT
Figure
FAULT PIN
CLEAR BY WRITING 1 TO FTACK
15-11. Clearing the FFLAG event bit will not enable the PWMs in automatic mode.
PWM(S) ENABLED
Figure 15-11. PWM Disabling in Automatic Mode
Figure 15-10. PWM Disabling Scheme
SHOT
ONE
CYCLE START
MC68HC908LB8 Data Sheet, Rev. 1
FMODE
PWM(S) DISABLED (INACTIVE)
R
S
Q
FFLAG
MANUAL
MODE
MODE
AUTO
FINT1
PWM(S) ENABLED
FAULT PIN DISABLE
R
S
Freescale Semiconductor
INTERRUPT REQUEST
Q
PWM DISABLE