MPC563XM Reference Manual, Rev. 1
684
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
Figure 22-56. OPWFMB Mode from 100% to 0% Duty Cycle
A 0% duty cycle signal is generated if A1=$0 as shown in
cycle 9. In this case B1=$8 match
from cycle 8 occurs at the same time as the A1=$0 match from cycle 9. Please, refer to
description of the A1 and B1 match generation. In this case A1 match has precedence over B1 match and
the output signal transitions to EDPOL.
22.5.1.1.15
Center Aligned Output Pulse Width Modulation with Dead-Time (OPWMC)
Mode
This operation mode generates a center aligned PWM with dead time insertion in the leading
(MODE[0:6]=00111b1) or trailing edge (MODE[0:6]=00111b0).
The selected counter bus must be running an up/down time base, as shown in
select the time base. Register A1 contains the ideal duty cycle for the PWM signal and is compared with
the selected time base. Register B1 contains the dead time value and is compared with the internal counter.
For a leading edge dead time insertion, the output PWM duty cycle is equal to the difference between
register A1 and register B1, and for a trailing edge dead time insertion, the output PWM duty cycle is equal
to the sum of register A1 and register B1. Mode[6] bit selects between trailing and leading dead time
insertion, respectively.
NOTE
The internal counter may be running in the internal prescaler ratio, while
the selected time base may be running in a different prescaler ratio. The
output signal may produce an unexpected output if the dead time interval is
greater than the duty cycle of the PWM signal.
When OPWMC mode is entered, coming out from GPIO mode, the output flip-flop is set to the
complement of the EDPOL bit in the EMIOSC[n] register.
When operating with leading edge dead time insertion, the first match between A1 and the selected time
base clears the internal counter and switches the selected time base to the internal counter. When a match
occurs between register B1 and the selected time base, the output flip-flop is set to the value of the EDPOL
bit and the time base is switched to the selected counter bus. In the next match between register A1 and
the selected time base, the output flip-flop is set to the complement of the EDPOL bit. This sequence
repeats continuously.
$000008
$000007
$000006
$000005
$000004
$000003
$000002
$000001
$000000
0%
100%
EMIOSCNT
EDPOL = 0
A1 value
B1 value
Output pin
$000008
Prescaler ratio = 1
cycle 1
cycle 2
cycle 3
cycle 4
cycle 5
cycle 6
cycle 7
cycle 8
cycle 9
$000007
$000006
$000005
$000004
$000003
$000002
$000001
$000000
A2 value
$000008
$000001
Содержание MPC5632M
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