
SPRS457E
– MARCH 2009 – REVISED JUNE 2011
6.19
Pulse Width Modulator (PWM)
The pulse width modulator (PWM) feature is very common in embedded systems. It provides a way to
generate a pulse periodic waveform for motor control or can act as a digital-to-analog converter with some
external components. This PWM peripheral is basically a timer with a period counter and a first-phase
duration comparator, where bit width of the period and first-phase duration are both programmable. The
Pulse Width Modulator (PWM) modules support the following features:
32-bit period counter
32-bit first-phase duration counter
8-bit repeat count for one-shot operation. One-shot operation will produce N + 1 periods of the
waveform, where N is the repeat counter value.
Configurable to operate in either one-shot or continuous mode
Buffered period and first-phase duration registers
One-shot operation triggerable by hardware events with programmable edge transitions. (low-to-high or
high-to-low).
One-shot operation triggerable by the ISIF VSYNC output of the video processing subsystem (VPSS),
which allows any of the PWM instantiations to be used as a ISIF timer. This allows the device module
to support the functions provided by the ISIF timer feature (generating strobe and shutter signals).
One-shot operation generates N+1 periods of waveform, N being the repeat count register value
Configurable PWM output pin inactive state
Interrupt and EDMA synchronization events
6.19.1 PWM Peripheral Register Description(s)
Table 6-85 lists the PWM registers, their corresponding acronyms, and the device memory locations
(offsets).
Table 6-85. Pulse Width Modulator (PWM) Registers
Offset
Acronym
Register Description
00h
PID
PWM Peripheral Identification Register
04h
PCR
PWM Peripheral Control Register
08h
CFG
PWM Configuration Register
0Ch
START
PWM Start Register
10h
RPT
PWM Repeat Count Register
14h
PER
PWM Period Register
18h
PH1D
PWM First-Phase Duration Register
6.19.2 PWM0/1/2/3 Electrical/Timing Data
Table 6-86. Switching Characteristics Over Recommended Operating Conditions for PWM0/1/2/3
DEVICE
NO.
PARAMETER
UNIT
MIN
MAX
1
tw(PWMH)
Pulse duration, PWMx high
37
ns
2
tw(PWML)
Pulse duration, PWMx low
37
ns
3
tt(PWM)
Transition time, PWMx
5
ns
4
td(ISIF-PWMV)
Delay time, ISIF(VD) trigger event to PWMx valid
0
10
ns
(1)
P = MXI1/CLKIN cycle time in ns. For example, when MXI1/CLKIN frequency is 24 MHz use P = 41.6 ns.
Copyright
2009–2011, Texas Instruments Incorporated
Peripheral Information and Electrical Specifications
183