MC68HC705CT4 Datasheet, PDF (95/152 Pages) Freescale Semiconductor, Inc – General Release Specification

Freescale Semiconductor, Inc.
Pulse Width Modulator (PWM)
Functional Description
12.3 Functional Description
A $00 in the PWM data register yields an off output (0%), but a $3F
yields a duty of 63/64 (98.4%).
When not in use, the PWM system can be shut off to save power by
clearing the PWME bit in MISCR.
Writes to the PWM data register can be performed at any time without
affecting the current PWM output signal. Updates on the PWM output
occur at the end of the PWM period (E x 64). At this time, the new value
is loaded into the PWM data register. If a write to the registers is
performed while the PWM is disabled, data is transferred directly to the
PWM register. A read of the data register reads the active count in
progress, not the buffered value.
After the PWM is enabled (PWM = 1) the PWM output remains low for
one E cycle. This allows synchronization and will not occur again until
the next time the PWM is enabled.
64 x E
10
3F
20
0
Figure 12-2. PWM Waveforms
MC68HC705CT4 — Rev. 2.0
MOTOROLA
General Release Specification
Pulse Width Modulator (PWM)
95
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