ePWM Submodules
664
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
C28 Enhanced Pulse Width Modulator (ePWM) Module
7.2.4.3
Action-Qualifier Event Priority
It is possible for the ePWM action qualifier to receive more than one event at the same time. In this case
events are assigned a priority by the hardware. The general rule is events occurring later in time have a
higher priority and software forced events always have the highest priority. The event priority levels for up-
down-count mode are shown in
. A priority level of 1 is the highest priority and level 7 is the
lowest. The priority changes slightly depending on the direction of TBCTR.
Table 7-10. Action-Qualifier Event Priority for Up-Down-Count Mode
Priority Level
Event If TBCTR is Incrementing
TBCTR = Zero up to TBCTR = TBPRD
Event If TBCTR is Decrementing
TBCTR = TBPRD down to TBCTR = 1
1 (Highest)
Software forced event
Software forced event
2
Counter equals CMPB on up-count (CBU)
Counter equals CMPB on down-count (CBD)
3
Counter equals CMPA on up-count (CAU)
Counter equals CMPA on down-count (CAD)
4
Counter equals zero
Counter equals period (TBPRD)
5
Counter equals CMPB on down-count (CBD)
Counter equals CMPB on up-count (CBU)
6 (Lowest)
Counter equals CMPA on down-count (CAD)
Counter equals CMPA on up-count (CBU)
shows the action-qualifier priority for up-count mode. In this case, the counter direction is
always defined as up and thus down-count events will never be taken.
Table 7-11. Action-Qualifier Event Priority for Up-Count Mode
Priority Level
Event
1 (Highest)
Software forced event
2
Counter equal to period (TBPRD)
3
Counter equal to CMPB on up-count (CBU)
4
Counter equal to CMPA on up-count (CAU)
5 (Lowest)
Counter equal to Zero
shows the action-qualifier priority for down-count mode. In this case, the counter direction is
always defined as down and thus up-count events will never be taken.
Table 7-12. Action-Qualifier Event Priority for Down-Count Mode
Priority Level
Event
1 (Highest)
Software forced event
2
Counter equal to Zero
3
Counter equal to CMPB on down-count (CBD)
4
Counter equal to CMPA on down-count (CAD)
5 (Lowest)
Counter equal to period (TBPRD)
It is possible to set the compare value greater than the period. In this case the action will take place as
shown in
Table 7-13. Behavior if CMPA/CMPB is Greater than the Period
Counter Mode
Compare on Up-Count Event
CAD/CBD
Compare on Down-Count Event
CAD/CBD
Up-Count Mode
If CMPA/CMPB
≤
TBPRD period, then the event
occurs on a compare match (TBCTR=CMPA or
CMPB).
Never occurs.
If CMPA/CMPB > TBPRD, then the event will not
occur.