Z8 Encore!® Motor Control Flash MCUs
Product Specification
74
PWM Timer and Fault Interrupts
The PWM generates interrupts to the eZ8 CPU upon any of the following events:
PWM Reload. The interrupt is generated at the end of a PWM period when a PWM regis-
ter reload occurs (the READYbit is set).
PWM Fault. A fault condition is indicated by asserting any of the FAULT pins, or by the
assertion of the comparator.
Fault Detection and Protection
The Z8FMC16100 Series Flash MCU contains hardware and software fault controls that
allow rapid deassertion of all enabled PWM output signals. A logic Low on an external
fault pin (FAULT0 or FAULT1), or the assertion of the overcurrent comparator, forces the
PWM outputs to a predefined OFF state.
Similar deassertion of the PWM outputs can be accomplished in software by writing to the
PWMOFFbit in the PWM Control 0 Register. The PWM counter continues to operate while
the outputs are deasserted (made inactive) due to one of these fault conditions.
The fault inputs can be individually enabled through the PWM Fault Control Register. If a
fault condition is detected and the source is enabled, a fault interrupt is generated. The
PWM Fault Status Register (PWMFSTAT) is read to determine which fault source has
caused the interrupt.
After a fault has been detected, and after the PWM outputs are disabled, modulator control
of the PWM outputs can be reenabled either by software, or by deassertion of the FAULT
input signal. Selection of either method is made via the PWM Fault Control Register
(PWMFCTL). Configuration of the fault modes and reenable methods allows pulse-by-
pulse limiting and hard shutdown. When configured in automatic restart mode, the PWM
outputs are reengaged at beginning of the next PWM cycle (the master timer value is equal
to 0) if all fault signals are deasserted. In a software-controlled restart, all fault inputs must
be deasserted and all fault flags cleared.
The fault input pin is Schmitt-triggered. The input signal from the pin, as well as the com-
parators, pass though an analog filter to reject high-frequency noise.
The logic path from the fault sources to the PWM outputs is asynchronous, which ensures
that the fault inputs will force the PWM outputs to their OFF state, even if the system
clock is stopped.
PWM Operation in CPU Halt Mode
When the eZ8 CPU is operating in HALT mode, the Pulse-Width Modulator continues to
operate, if enabled. To minimize the current in HALT mode, the Pulse-Width Modulator
must be disabled by clearing the PWMENbit to 0.
Pulse-Width Modulator
P R E L I M I N A R Y
PS024604-1005
ZILOG [ ZILOG, INC. ]
