Texas Instruments TMS320x28xx, 28xxx manual Action-Qualifier Event Priority

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Action-Qualifier (AQ) Submodule

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 Table 2-8. 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 2-8. 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

2Counter equals CMPB on up-count (CBU)

3Counter equals CMPA on up-count (CAU)

4Counter equals zero

5Counter equals CMPB on down-count (CBD)

6 (Lowest) Counter equals CMPA on down-count (CAD)

Software forced event

Counter equals CMPB on down-count (CBD)

Counter equals CMPA on down-count (CAD)

Counter equals period (TBPRD)

(1)Counter equals CMPB on up-count (CBU) (1)

(1) Counter equals CMPA on up-count (CBU) (1)

(1)To maintain symmetry for up-down-count mode, both up-events (CAU/CBU) and down-events (CAD/CBD) can be generated for TBPRD. Otherwise, up-events can occur only when the counter is incrementing and down-events can occur only when the counter is decrementing.

Table 2-9shows 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 2-9. 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

Table 2-10shows 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 2-10. 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 2-11.

40 ePWM Submodules SPRU791D–November 2004–Revised October 2007

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