3.2.9.3.2 Event Filtering
The DCAEVT1/2 and DCBEVT1/2 events can be filtered via event filtering logic to remove noise by optionally
blanking events for a certain period of time. This is useful for cases where the analog comparator outputs may
be selected to trigger DCAEVT1/2 and DCBEVT1/2 events, and the blanking logic is used to filter out potential
noise on the signal prior to tripping the PWM outputs or generating an interrupt or ADC start-of-conversion. The
event filtering can also capture the TBCTR value of the trip event.
shows the details of the event
filtering logic.
DCAEVT1
DCFOFFSET[OFFSET]
Sync
Blank
Control
Logic
DCFWINDOW[WINDOW]
DCFCTL[BLANKE, PULSESEL]
DCCAP[15:0] Reg
DCAEVT2
DCBEVT1
DCBEVT2
00
01
10
11
DCFCTL[PULSESEL]
TBCTR(16)
Capture
Control
Logic
CTR = PRD
CTR = 0
TBCLK
CTR=PRD
CTR=Zero
TBCLK
TBCLK
DCEVTFILT
async
DCFCTL[SRCSEL]
1 0
BLANKWDW
DCFCTL[INVERT]
DCCAPCTL[CAPE, SHDWMODE]
Figure 3-50. Event Filtering
If the blanking logic is enabled, one of the digital compare events – DCAEVT1, DCAEVT2, DCBEVT1,
DCBEVT2 – is selected for filtering. The blanking window, which filters out all event occurrences on the
signal while it is active, will be aligned to either a CTR = PRD pulse or a CTR = 0 pulse (configured by the
DCFCTL[PULSESEL] bits). An offset value in TBCLK counts is programmed into the DCFOFFSET register,
which determines at what point after the CTR = PRD or CTR = 0 pulse the blanking window starts. The
duration of the blanking window, in number of TBCLK counts after the offset counter expires, is written to the
DCFWINDOW register by the application. During the blanking window, all events are ignored. Before and after
the blanking window ends, events can generate soc, sync, interrupt, and force signals as before.
illustrates several timing conditions for the offset and blanking window within an ePWM period.
Notice that if the blanking window crosses the CTR = 0 or CTR = PRD boundary, the next window still starts at
the same offset value after the CTR = 0 or CTR = PRD pulse.
Enhanced Pulse Width Modulator (ePWM) Module
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
301
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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