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Event
register
(ER)
Event
enable
register
(EER)
Event
set
register
(ESR)
Chained
event
register
(CER)
QDMA
event
register
(QER)
32
32
32
8
Queue 0
Event
queues
Queue bypass
Parameter
set 0
Parameter
set 1
set 127
Parameter
Parameter
set 126
PaRAM
E31
E0
E1
From
EDMA3TC(s)
Completion
interface
Completion
detection
Event
trigger
Manual
trigger
Chain
trigger
QDMA trigger
Completion
interrupt
detection
Error
Error Interrupt
Transfer Completion
Interrupts
EDMA3 channel
controller
From peripherals/external events
Trigger source priority
Dequeue priority
Channel priority
15
0
Queue 1
15
0
To
EDMA3TC(s)
T
ransferrequestsubmission
Channelmapping
32:1priorityencoder
8:1priorityencoder
Architecture
619
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Enhanced Direct Memory Access (EDMA3) Controller
17.2.13 EDMA3 Prioritization
The EDMA3 controller has many implementation rules to deal with concurrent events/channels, transfers,
etc. The following subsections detail various arbitration details whenever there might be occurrence of
concurrent activity.
shows the different places EDMA3 priorities come into play.
17.2.13.1 Channel Priority
The DMA event register (ER) captures all external/peripheral events connected to the EDMA3CC;
likewise, the QDMA event register (QER) captures QDMA events for all QDMA channels; therefore, it is
possible for events to occur simultaneously on the DMA/QDMA event inputs. For events arriving
simultaneously, the event associated with the lowest channel number is prioritized for submission to the
event queues (for DMA events, channel 0 has the highest priority and channel 31 has the lowest priority;
similarly, for QDMA events, channel 0 has the highest priority and channel 7 has the lowest priority). This
mechanism only sorts simultaneous events for submission to the event queues.
If a DMA and QDMA event occurs simultaneously, the DMA event always has prioritization against the
QDMA event for submission to the event queues.
Figure 17-14. EDMA3 Prioritization