
PULSE WIDTH MODULATION TIMER
10-8
10.5.5
Polarity Select Register (PWPOL)
Each channel has a polarity bit (PPOLx) to start the cycle with a high signal or with a low signal. This
is shown on the block diagram as a multiplex select of either the Q output or the Q output of the PWM
output flip-flop. When one of the bits in the PWPOL register is set, the associated PWM channel
output is high at the beginning of the clock cycle, then goes low when the duty count is reached.
PCLK4
PCLK3
PCLK2
PCLK1
PWPOL
$1061
7
6
5
4
3
2
1
0
RESET:
PPOL4
PPOL3
PPOL2
PPOL1
0
READ:
Any time.
WRITE:
Any time.
RESET:
$00
PCLK4 — Pulse Width Channel 4 Clock Select
1 – The clock source for PWM channel 4 is Clock S. (Clock S equals Clock A divided
by two times the value (plus one) in the PWSCAL register.)
0 – Clock B is the clock source for PWM channel 4.
PCLK3 — Pulse Width Channel 3 Clock Select
1 – The clock source for PWM channel 3 is Clock S.
0 – Clock B is the clock source for PWM channel 3.
PCLK2 — Pulse Width Channel 2 Clock Select
1 – The clock source for PWM channel 2 is Clock S.
0 – Clock A is the clock source for PWM channel 2.
PCLK1 — Pulse Width Channel 1 Clock Select
1 – The clock source for PWM channel 1 is Clock S.
0 – Clock A is the clock source for PWM channel 1.
Note:
While register bits PCLK1 – 4 may be written at any time, if a clock select is changed while
a PWM signal is being generated, a truncated pulse may occur during the transition.
PPOL4 — Pulse Width Channel 4 Polarity
1 – PWM channel 4 output is high at the beginning of the clock cycle, then goes low
when the duty count is reached.
0 – PWM channel 4 output is low at the beginning of the clock cycle, then goes high
when the duty count is reached.
Freescale
Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
nc.
..
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:
MC68HC11G5,
MC68HC11G7,
MC68HC711G5