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LOAD
0
COMPB
COMPA
load
zero
cmpB
cmpA
dir
ADown
BDown
Functional Description
1439
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Pulse Width Modulator (PWM)
21.3.3 PWM Comparators
Each PWM generator has two comparators that monitor the value of the counter; when either comparator
matches the counter, they output a single-clock-cycle-width High pulse, labeled
cmpA
and
cmpB
in the
figures in this chapter. When in Count-Up/Down mode, these comparators match both when counting up
and when counting down, and thus are qualified by the counter direction signal. These qualified pulses are
used in the PWM generation process. If either comparator match value is greater than the counter load
value, then that comparator never outputs a high pulse.
shows the behavior of the counter and the relationship of these pulses when the counter is in
Count-Down mode.
shows the behavior of the counter and the relationship of these pulses
when the counter is in Count-Up/Down mode. In these figures, the following definitions apply:
•
LOAD is the value in the PWMnLOAD register
•
COMPA is the value in the PWMnCMPA register
•
COMPB is the value in the PWMnCMPB register
•
0 is the value zero
•
load is the internal signal that has a single-clock-cycle-width High pulse when the counter is equal to
the load value
•
zero is the internal signal that has a single-clock-cycle-width High pulse when the counter is zero
•
cmpA is the internal signal that has a single-clock-cycle-width High pulse when the counter is equal to
COMPA
•
cmpB is the internal signal that has a single-clock-cycle-width High pulse when the counter is equal to
COMPB
•
dir is the internal signal that indicates the count direction
Figure 21-3. PWM Count Down Mode