mc68hc908lb8 Freescale Semiconductor, Inc, mc68hc908lb8 Datasheet - Page 149

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

15.4.3 Output Polarity
The output polarity of the PWMs is determined by the POLx bits. Positive polarity means that when the
PWM is active, the PWM output is high. Conversely, negative polarity means that when the PWM is
active, PWM output is low. See
15.5 Fault Protection
Conditions may arise in the external drive circuitry which require that the PWM signals become inactive
immediately. 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 the
external fault pin or by writing a logic high to either of the disable bits (DIS0 and DIS1 in PWM control
register 1).
disabled, they are forced to their inactive state. The PWM generator continues
A fault can also generate a CPU interrupt. The fault pin has its own interrupt vector.
15.5.1 Fault Condition Input Pin
A logic high level on a fault pin disables the PWM(s) determined by the disable map bits (MAPx). The
external fault pin is software-configurable to re-enable the PWMs either with the fault pin (automatic
Freescale Semiconductor
Figure 15-10
The terms “active” and “inactive” refer to the asserted and negated states
of the PWM signals and should not be confused with the high-impedance
state of the PWM pins.
PWMVALxH:PWMVALxL
$0000–$0FFF
$1000–$7FFF
$8000–$FFFF
Table 15-3. PWM Data Overflow and Underflow Conditions
UP-ONLY COUNTER
EDGE-ALIGNED POSITIVE POLARITY
shows the structure of the PWM disabling scheme. While the PWM pins are
MODULUS = 4
PWM <= 0
PWM >= 4
PWM = 1
PWM = 2
PWM = 3
Figure
Figure 15-9. PWM Output Polarity
MC68HC908LB8 Data Sheet, Rev. 1
15-9.
Condition
Underflow
Overflow
NOTE
Normal
EDGE-ALIGNED NEGATIVE POLARITY
MODULUS = 4
PWM <= 0
PWM >= 4
PWM = 1
PWM = 2
PWM = 3
Per register contents
PWM Value Used
$FFF
$000
Fault Protection
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