3.4.3 Continuous Operation
3.4.3.1
Receive Channel
3.4.3.2
Transmit Channel
1180 0000h
A4i
A12i
A3i
A2i
A1i
A9i
A10i A11i
A7i
A6i
A5i
A13i
...
...
A8i
RSR
RBR
DRR
REVT
B6i
B9i
B10i B11i B12i B13i
...
B1i
B2i
B3i
B4i
B5i
...
B8i
B7i
..B5..A5..B4..A4..B3..A3..B2..A2..B1..A1
01E0 2000h
1180 0080h
B6o
A6o
B2o
B1o
B9o B10o
A9i
A10i
B5o
B4o
B3o
B11o B12o B13o
...
A11i A12i A13i
...
A1o
A2o
A3o
A4o
A5o
B7o
B8o
...
...
A8o
A7o
1180 1000h
1180 1080h
01E0 2004h
DXR
A1..B1..A2..B2..A3..B3..A4..B4..A5..B5
XSR
XEVT
Peripheral Servicing Example
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Configuring a DMA channel to receive a single frame of data is useful, and is applicable to some systems.
A majority of the time, however, data is going to be continuously transmitted and received throughout the
entire operation of the CPU. In this case, it is necessary to implement some form of linking such that the
DMA channels continuously reload the necessary parameter sets. In this example, the ASP is configured
to transmit and receive data on a array. To simplify the example, only two channels are active for both
transmit and receive data streams. Each channel receives packets of 128 elements. The packets are
transferred from the serial port to L2 memory and from L2 memory to the serial port, as shown in
The ASP generates REVT for every element received and generates XEVT for every element transmitted.
To service the data streams, DMA channels 12 and 13 must be set up for 1D-to-1D transfers with
A-synchronization.
shows the parameters for the parameter entries for the channel for these transfers. In order to
service the ASP continuously throughout CPU operation, the channels must be linked to a duplicate
PaRAM set in the PaRAM. After all frames have been transferred, the DMA channels reload and continue.
shows the reload parameters for the channel.
DMA channel 3 services the incoming data stream of the ASP. The source address is set to that of the
data receiver register (DRR), and the destination address is set to the first element of the data block.
Since there are two data channels being serviced, A and B, they are to be located separately within the
L2 SRAM.
In order to facilitate continuous operation, a copy of the PaRAM set for the channel is placed in PaRAM
set 64. The LINK option is set and the link address is provided in the PaRAM set. Upon exhausting the
channel 3 parameter set, the parameters located at the link address are loaded into the channel 3
parameter set and operation continues. This function continues throughout device operation until halted by
the CPU.
DMA channel 2 services the outgoing data stream of the ASP. In this case the destination address needs
no update, hence, the parameter set changes accordingly. Linking is also used to allow continuous
operation by the DMA channel, with duplicate PaRAM set entries at PaRAM set 65.
Figure 3-11. Servicing Continuous ASP Data Example
EDMA3 Transfer Examples
76
SPRUG34 – November 2008
Содержание TMS320DM357
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