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PWMnCMPA
Comparators
PWMnCMPB
PWMnLOAD
Timer
PWMnCOUNT
PWMnDBCTL
Dead-Band
Generator
PWMnDBRISE
PWMnDBFALL
PWMnCTL
Control
PWMnFLTSRC0
Fault Condition
PWMnFLTSRC1
PWMnMINFLTPER
PWMnFLTSEN
PWMnFLTSTAT0
PWMnFLTSTAT1
PWM Clock
PWM Generator Block
Signal Generator
PWMnGENA
PWMnGENB
PWMnINTEN
Interrupt and
Trigger
Generator
PWMnRIS
PWMnISC
Digital Trigger(s)
Fault(s)
SZP$¶
SZP%¶
Interrupts /
Triggers
pwmfault
cmpA
cmpB
zero
load
dir
pwmA
pwmB
Functional Description
1438
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Pulse Width Modulator (PWM)
Figure 21-2. PWM Generator Block Diagram
21.3 Functional Description
21.3.1 Clock Configuration
The PWM has two clock source options:
•
The system clock
•
A predivided system clock
The clock source is selected by programming the USEPWM bit in the PWM Clock Configuration
(PWMCC) register. The PWMDIV bit field specifies the divisor of the System Clock that is used to create
the PWM Clock.
21.3.2 PWM Timer
The timer in each PWM generator runs in one of two modes: Count-Down mode or Count-Up/Down mode.
In Count-Down mode, the timer counts from the load value to zero, goes back to the load value, and
continues counting down. In Count-Up/Down mode, the timer counts from zero up to the load value, back
down to zero, back up to the load value, and so on. Generally, Count-Down mode is used for generating
left- or right-aligned PWM signals, while the Count-Up/Down mode is used for generating center-aligned
PWM signals.
The timers output three signals that are used in the PWM generation process: the direction signal (this is
always Low in Count-Down mode, but alternates between Low and High in Count-Up/Down mode), a
single-clock-cycle-width High pulse when the counter is zero, and a single-clock-cycle-width High pulse
when the counter is equal to the load value. Note that in Count-Down mode, the zero pulse is immediately
followed by the load pulse. In the figures in this chapter, these signals are labelled
dir
,
zero
, and
load
.