Functional Description
11.3.14.2 Trigger Source Priority
If a DMA channel is associated with more than one trigger source (event trigger, manual trigger, and chain
trigger), and if multiple events are set simultaneously for the same channel (ER.En = 1, ESR.En = 1 ,
CER.En = 1) , then the EDMA3CC always services these events in the following priority order: event
trigger (via ER) is higher priority than chain trigger (via CER) and chain trigger is higher priority than
manual trigger (via ESR).
This implies that if for channel 0, both ER.E0 = 1 and CER.E0 = 1 at the same time, then the ER.E0 event
is always queued before the CER.E0 event.
11.3.14.3 Dequeue Priority
The priority of the associated transfer request (TR) is further mitigated by which event queue is being used
for event submission (dictated by DMAQNUM and QDMAQNUM). For submission of a TR to the transfer
request, events need to be de-queued from the event queues. Queue 0 has the highest dequeue priority
and queue 3 the lowest.
11.3.14.4
System (Transfer Controller) Priority
INIT_PRIORITY_0 and INIT_PRIORITY_1 registers in the chip configuration module are used to configure
the EDMA TC's priority through the system bus infrastructure. Additionally, the priority settings for DDR
memory accesses are defined in the dynamic memory manager (DMM).
NOTE:
The default priority for all TCs is the same, 0 or highest priority relative to other masters. It is
recommended that this priority be changed based on system level considerations, such as
real-time deadlines for all masters including the priority of the transfer controllers with respect
to each other.
11.3.15 EDMA3 Operating Frequency (Clock Control)
The EDMA3 channel controller and transfer controller are clocked from PLL_L3 SYSCLK4. The EDMA3
system runs at the L3 clock frequency.
11.3.16 Reset Considerations
A hardware reset resets the EDMA3 (EDMA3CC and EDMA3TC) and the EDMA3 configuration registers.
The PaRAM memory contents are undefined after device reset and you should not rely on parameters to
be reset to a known state. The PaRAM entry must be initialized to a desired value before it is used.
11.3.17 Power Management
The EDMA3 (EDMA3CC and EDMA3TC) can be placed in reduced-power modes to conserve power
during periods of low activity. The power management of the peripheral is controlled by the power reset
clock management (PRCM). The PRCM acts as a master controller for power management for all
peripherals on the device.
The EDMA3 controller can be idled on receiving a clock stop request from the PRCM. The requests to
EDMA3CC and EDMA3TC are separate. In general, it should be verified that there are no pending
activities in the EDMA3 controller
11.3.18 Emulation Considerations
During debug when using the emulator, the CPU(s) may be halted on an execute packet boundary for
single-stepping, benchmarking, profiling, or other debug purposes. During an emulation halt, the EDMA3
channel controller and transfer controller operations continue. Events continue to be latched and
processed and transfer requests continue to be submitted and serviced.
918
Enhanced Direct Memory Access (EDMA)
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated