3.4.5 Transfer Chaining Examples
3.4.5.1
Servicing Input/Output FIFOs with a Single Event
Peripheral Servicing Example
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Figure 3-17. Ping-Pong Buffering for ASP Example Ping PaRAM
(a) EDMA Ping Parameters for Channel 3 at Set 65 Linked to Set 64
Parameter Contents
Parameter
0010 D000h
Channel Options Parameter (OPT)
01E0 2000h
Channel Source Address (SRC)
0080h
0001h
Count for 2nd Dimension (BCNT)
Count for 1st Dimension (ACNT)
1180 0000h
Channel Destination Address (DST)
0001h
0000h
Destination BCNT Index (DSTBIDX)
Source BCNT Index (SRCBIDX)
0080h
4800h
BCNT Reload (BCNTRLD)
Link Address (LINK)
0000h
0000h
Destination CCNT Index (DSTCIDX)
Source CCNT Index (SRCCIDX)
0000h
0001h
Reserved
Count for 3rd Dimension (CCNT)
(b) EDMA Ping Parameters for Channel 2 at Set 67 Linked to Set 66
Parameter Contents
Parameter
0010 C000h
Channel Options Parameter (OPT)
1180 1000h
Channel Source Address (SRC)
0080h
0001h
Count for 2nd Dimension (BCNT)
Count for 1st Dimension (ACNT)
01E0 2004h
Channel Destination Address (DST)
0000h
0001h
Destination BCNT Index (DSTBIDX)
Source BCNT Index (SRCBIDX)
0080h
4840h
BCNT Reload (BCNTRLD)
Link Address (LINK)
0000h
0000h
Destination CCNT Index (DSTCIDX)
Source CCNT Index (SRCCIDX)
0000h
0001h
Reserved
Count for 3rd Dimension (CCNT)
The following examples explain the intermediate transfer complete chaining function.
Many systems require the use of a pair of external FIFOs that must be serviced at the same rate. One
FIFO buffers data input, and the other buffers data output. The EDMA3 channels that service these FIFOs
can be set up for AB-synchronized transfers. While each FIFO is serviced with a different set of
parameters, both can be signaled from a single event. For example, an external interrupt pin can be tied
to the status flags of one of the FIFOs. When this event arrives, the EDMA3 needs to perform servicing for
both the input and output streams. Without the intermediate transfer complete chaining feature this would
require two events, and thus two external interrupt pins. The intermediate transfer complete chaining
feature allows the use of a single external event (for example, a GPIO event).
shows the
EDMA3 setup and illustration for this example.
A GPIO event (in this case, GPINT0) triggers an array transfer. Upon completion of each intermediate
array transfer of channel 32, intermediate transfer complete chaining sets the E63 bit (specified by TCC of
63) in the chained event register high (CERH) and provides a synchronization event to channel 63. Upon
completion of the last array transfer of channel 32, transfer complete chaining—not intermediate transfer
complete chaining—sets the E63 bit in CERH (specified by TCCMODE:TCC) and provides a
synchronization event to channel 63. The completion of channel 63 sets the I63 bit (specified by
TCCMODE:TCC) in the interrupt pending register high (IPRH), which can generate an interrupt to the
CPU, if the I63 bit in the interrupt enable register high (IERH) is set to 1.
82
EDMA3 Transfer Examples
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