LM3S611-IQN50-C2T Datasheet, PDF (485/574 Pages) Texas Instruments – Stellaris® LM3S611 Microcontroller

NRND: Not recommended for new designs.
Stellaris^® LM3S611 Microcontroller
Figure 14-4. PWM Count-Up/Down Mode
Load
CompA
CompB
Zero
Load
Zero
A
B
Dir
14.3.3
BUp
AUp
BDown
ADown
PWM Signal Generator
The PWM generator takes these pulses (qualified by the direction signal), and generates two PWM
signals. In Count-Down mode, there are four events that can affect the PWM signal: zero, load,
match A down, and match B down. In Count-Up/Down mode, there are six events that can affect
the PWM signal: zero, load, match A down, match A up, match B down, and match B up. The match
A or match B events are ignored when they coincide with the zero or load events. If the match A
and match B events coincide, the first signal, PWMA, is generated based only on the match A event,
and the second signal, PWMB, is generated based only on the match B event.
For each event, the effect on each output PWM signal is programmable: it can be left alone (ignoring
the event), it can be toggled, it can be driven Low, or it can be driven High. These actions can be
used to generate a pair of PWM signals of various positions and duty cycles, which do or do not
overlap. Figure 14-5 on page 485 shows the use of Count-Up/Down mode to generate a pair of
center-aligned, overlapped PWM signals that have different duty cycles.
Figure 14-5. PWM Generation Example In Count-Up/Down Mode
Load
CompA
CompB
Zero
PWMA
PWMB
In this example, the first generator is set to drive High on match A up, drive Low on match A down,
and ignore the other four events. The second generator is set to drive High on match B up, drive
Low on match B down, and ignore the other four events. Changing the value of comparator A
changes the duty cycle of the PWMA signal, and changing the value of comparator B changes the
duty cycle of the PWMB signal.
June 18, 2012
485
Texas Instruments-Production Data