Stream A Destination Address A4i
A12i
A3iA2iA1i
A9i A10i A11i
A7iA6iA5i
A13i ... ...
A8i
RSR DAT
AREVT
B6i
B9i B10i B11i B12i B13i ...
B1i B2i B3i B4i B5i
...
B8i
B7i
..B5..A5..B4..A4..B3..A3..B2..A2..B1..A1 McASP RX Register
Stream B Destination Address
B6o
A6o
B2oB1o
B9o B10o
A9o A10o
B5oB4oB3o
B11o B12o B13o ...
A11o A12o A13o ...
A1o A2o A3o A4o A5o
B7o B8o
...
...
A8oA7oStream A Source Address
Stream B Source Address
McASP TX Register
DAT
A1..B1..A2..B2..A3..B3..A4..B4..A5..B5
XSR
AXEVT
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Functional Description
11.3.19.4.3 Continuous Operation
Configuring an EDMA3 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 processor. In this case, it is necessary to implement some form of
linking such that the EDMA3 channels continuously reload the necessary parameter sets. In this example,
McASP is configured to transmit and receive data on a T1 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 internal memory and from internal
memory to the serial port, as shown Figure 11-32.
The McASP generates AREVT for every element received and generates AXEVT for every element
transmitted. To service the data streams, the DMA channels associated with the McASP must be setup for
1D-to-1D transfers with A-synchronization.
Figure 11-33 shows the parameter entries for the channel for these transfers. To service the McASP
continuously, the channels must be linked to a duplicate PaRAM set in the PaRAM. After all frames have
been transferred, the EDMA3 channels reload and continue. Figure 11-34 shows the reload parameters
for the channel.
11.3.19.4.3.1 Receive Channel
EDMA3 channel 15 services the incoming data stream of McASP. The source address is set to that of the
receive serializer buffer, and the destination address is set to the first element of the data block. Because
there are two data channels being serviced, A and B, they are to be located separately within the L2
SRAM.
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
15 parameter set, the parameters located at the link address are loaded into the channel 15 parameter set
and operation continues. This function continues throughout device operation until halted by the CPU.
11.3.19.4.3.2 Transmit Channel
EDMA3 channel 12 services the outgoing data stream of McASP. 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 EDMA3 channel, with duplicate PaRAM set entries at PaRAM set 65.
Figure 11-32. Servicing Continuous McASP Data Example
927
SPRUH73H–October 2011–Revised April 2013 Enhanced Direct Memory Access (EDMA)
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