Texas Instruments TMS570LC4357 User Manual

The above figure illustrates that by default Lower the channel number, higher the Priority.
Priority Queue
Ch0 Ch2 Ch3 Ch4...
Control Packet 0
Control Packet 1
Control Packet 2
Control Packet 3
Control Packet 4
Control Packet 5
Control Packet 6
Control Packet 7
Control Packet 8
Control Packet 9
Control Packet 10
Control Packet 11
Control Packet 12
Control Packet 13
Control Packet 14
Control Packet 15
Triggered Channels
ORDER
OF
PRIORITY
High
Low
0x0
0x40
E1
E2
E13
E4
E5
E16
E7
E8
E19E10
E11
E22
0x80
0x20
0x60
Element Index = 64
Frame Index = 4
Element Size = 32 bit
Element Count = 3
Frame Count = 8
E14 E17
E20
E23
E3
E6 E9
E12
E15 E18
E21
E23
This example can be applied to either source or
destination indexing and assumes the following setup.
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SPNU563A–March 2018
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Direct Memory Access Controller (DMA) Module
Figure 20-8. DMA Indexing Example 2
20.2.5 Priority Queue
User can assign channels in to priority queues to facilitate request handling during arbitration. The port
has two priority queues: a high and a low priority queue. Each queue can be configured to follow a fixed or
rotating priority scheme. Fixed priority is such that the lower the channel number (Figure 20-9), the higher
its priority. Rotating priority is based on a round-robin scheme. Initially, the priority list is sorted according
to the fixed priority scheme. Channels assigned to the high priority queue are always serviced first
according to the selected priority scheme before channels in the low priority queue are serviced. Table 20-
2 describes how arbitration is performed according to different priority schemes.
NOTE: Since the DMA controller provides the capability to map any one of the hardware DMA
request lines to any channel, the numerical order of the hardware DMA request does not
imply any priority. The priority of each hardware DMA request is programmed and
determined by software.
Figure 20-9. Fixed Priority Scheme

Texas Instruments TMS570LC4357 Specifications

General

Brand	Texas Instruments
Model	TMS570LC4357
Category	Microcontrollers
Language	English