MOTOROLA
PULSE WIDTH MODULATOR
MMC2001
15-8
REFERENCE MANUAL
15.3 PWM Operating Range
Table 15-3 shows the operating range and resolution of the PWM with a 16-MHz
HI_REFCLK. The minimum period range assumes a value of two in the period regis-
ter, while the maximum assumes a value of 256.
15.4 PWM Operation in Low-Power System Modes
Table 15-4 summarizes PWM operation in the different low-power modes.
In most modes, the PWM operates as long as a clock is available. In doze mode, the
PWM channels may be selectively disabled, depending on the value of the DOZE
control bit. PWM channel operation will be suspended at the end of the current
period. In stop mode, the PWM halts immediately (due to halting of system clocks)
and forgets the state of any period (the state machine is reset, and the shift register is
cleared). It is assumed that when stop is initiated, the channels have been disabled.
Table 15-3 PWM Range at 16 MHz
Divide By
Approximate Period
Range at 16 MHz
Resolution at
16 MHz
4
0.5
µ
s – 256
µ
s
.25
µ
s
8
1
µ
s – 512
µ
s
.5
µ
s
16
2
µ
s – 1 ms
1
µ
s
64
8
µ
s – 4.1 ms
4
µ
s
256
32
µ
s – 16.5 ms
16
µ
s
2048
256
µ
s – 65.6 ms
128
µ
s
16384
2 ms – 1 s
1 ms
65536
8.2 ms – 4 s
4.1 ms
Table 15-4 PWM Low-Power Mode Operation
Mode
Operation
Normal
Runs whenever enabled
Wait
Runs whenever enabled
Doze
If DOZE is set (in PWM control register),
then disabled.
Stop
Disabled
Freescale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
nc.
..