EFM32WG Datasheet, PDF (52/834 Pages) List of Unclassifed Manufacturers – The EFM32WG Wonder Gecko is the ideal choice for demanding 8-, 16-, and 32-bit energy sensitive applications.

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and this determines the arbitration rate. For example, if R = 4 then the arbitration rate is 2⁴, that is, the
controller arbitrates every 16 DMA transfers.
Table 8.1 (p. 52) lists the arbitration rates.
Table 8.1. AHB bus transfer arbitration interval
R_power
Arbitrate after x DMA transfers
b0000
x=1
b0001
x=2
b0010
x=4
b0011
x=8
b0100
x = 16
b0101
x = 32
b0110
x = 64
b0111
x = 128
b1000
x = 256
b1001
x = 512
b1010 - b1111 x = 1024
Note
You must take care not to assign a low-priority channel with a large R_power because this
prevents the controller from servicing high-priority requests, until it re-arbitrates.
The number of dma transfers N that need to be done is specified by the user. When N > 2^R and is not an
integer multiple of 2^R then the controller always performs sequences of 2^R transfers until N < 2^R remain
to be transferred. The controller performs the remaining N transfers at the end of the DMA cycle.
You store the value of the R_power bits in the channel control data structure. See Section 8.4.3.3 (p.
65) for more information about the location of the R_power bits in the data structure.
8.4.2.2 Priority
When the controller arbitrates, it determines the next channel to service by using the following
information:
• the channel number
• the priority level, default or high, that is assigned to the channel.
You can configure each channel to use either the default priority level or a high priority level by setting
the DMA_CHPRIS register.
Channel number zero has the highest priority and as the channel number increases, the priority of a
channel decreases. Table 8.2 (p. 52) lists the DMA channel priority levels in descending order of
priority.
Table 8.2. DMA channel priority
Channel
number
0
Priority level
setting
High
Descending order of
channel priority
Highest-priority DMA channel
2013-05-08 - Wonder Gecko Family - d0233_Rev0.50
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