RM0046 Enhanced Direct Memory Access (eDMA)
Doc ID 16912 Rev 5 401/936
Note: The TCD structures for the eDMA channels shown in Figure 193 are implemented in
internal SRAM. These structures are not initialized at reset. Therefore, all channel TCD
parameters must be initialized by the application code before activating that channel.
Table 193 gives a detailed description of the TCNn fields.
Figure 193. TCD structure
Word
Offset
0 1 2 3 4 5 6 7 8 9 10111213141516171819202122232425262728293031
0x0
SADDR
0x4
SMOD SSIZE DMOD DSIZE SOFF
0x8
NBYTES
0xC
SLAST
0x10
DADDR
0x14
CITER.E_ LINK
CITER
(1)
or
CITER.LINKCH
CITER
1
DOFF
0x18
DLAST_SGA
0x1C
BITER.E_ LINK
BITER
(2)
or
BITER.LINKCH
BITER
2
BWC MAJOR LINKCH
DONE
ACTIVE
MAJOR.E_LINK
E_SG
D_REQ
INT_HALF
INT_MAJ
START
1. If channel linking on minor link completion is disabled, TCD bits [161:175] form a 15-bit CITER field;
if channel-to-channel linking is enabled, CITER becomes a 9-bit field.
2. If channel linking on minor link completion is disabled, TCD bits [225:239] form a 15-bit BITER field;
if channel-to-channel linking is enabled, BITER becomes a 9-bit field.
Table 193. TCDn field descriptions
Bits
Word Offset
[n:n]
Field Name Description
0–31
0x0 [0:31]
SADDR
[0:31]
Source address. Memory address pointing to the source data.
Word 0x0, bits 0–31.
32–36
0x4 [0:4]
SMOD
[0:4]
Source address modulo.
0 Source address modulo feature is disabled.
not 0 This value defines a specific address range that is specified to be either the
value after SADDR + SOFF calculation is performed or the original register
value. The setting of this field provides the ability to easily implement a
circular data queue. For data queues requiring power-of-2 “size” bytes, start
the queue at a 0-modulo-size address and set the SMOD field to the value
for the queue, freezing the desired number of upper address bits. The value
programmed into this field specifies the number of lower address bits that are
allowed to change. For this circular queue application, the SOFF is typically
set to the transfer size to implement post-increment addressing with the
SMOD function constraining the addresses to a 0-modulo-size range.
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