RM0046 Enhanced Direct Memory Access (eDMA)
Doc ID 16912 Rev 5 403/936
161–166
0x14 [1:6]
CITER
[0:5]
or
CITER.LINKCH
[0:5]
Current “major” iteration count or link channel number.
If channel-to-channel linking is disabled (TCD.CITER.E_LINK = 0), then
– No channel-to-channel linking (or chaining) is performed after the inner minor
loop is exhausted. TCD bits [161:175] form a 15-bit CITER field.
otherwise
– After the minor loop is exhausted, the eDMA engine initiates a channel service
request at the channel defined by CITER.LINKCH[0:5] by setting that channel’s
TCD.START bit.
167–175
0x14 [7:15]
CITER
[6:14]
Current “major” iteration count. This 9 or 15-bit count represents the current major
loop count for the channel. It is decremented each time the minor loop is
completed and updated in the transfer control descriptor memory. After the major
iteration count is exhausted, the channel performs a number of operations (for
example, final source and destination address calculations), optionally generating
an interrupt to signal channel completion before reloading the CITER field from the
beginning iteration count (BITER) field.
When the CITER field is initially loaded by software, it must be set to the same value as
that contained in the BITER field.
If the channel is configured to execute a single service request, the initial values of
BITER and CITER must be 0x0001.
176–191
0x14 [16:31]
DOFF
[0:15]
Destination address signed offset. Sign-extended offset applied to the current
destination address to form the next-state value as each destination write is
completed.
192–223
0x18 [0:31]
DLAST_SGA
[0:31]
Last destination address adjustment or the memory address for the next transfer
control descriptor to be loaded into this channel (scatter/gather).
If scatter/gather processing for the channel is disabled (TCD.E_SG = 0) then
– Adjustment value added to the destination address at the completion of the
outer major iteration count.
This value can be applied to “restore” the destination address to the initial value, or
adjust the address to reference the next data structure.
Otherwise
– This address points to the beginning of a 0-modulo-32 byte region containing
the next transfer control descriptor to be loaded into this channel. This channel
reload is performed as the major iteration count completes. The scatter/gather
address must be 0-modulo-32 byte, otherwise a configuration error is reported.
Table 193. TCDn field descriptions (continued)
Bits
Word Offset
[n:n]
Field Name Description
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