Information

programmed in increments to match the transfer size: one byte for the source and four
bytes for the destination. The final source and destination addresses are adjusted to return
to their beginning values.
TCDn_CITER = TCDn_BITER = 1
TCDn_NBYTES = 16
TCDn_SADDR = 0x1000
TCDn_SOFF = 1
TCDn_ATTR[SSIZE] = 0
TCDn_SLAST = -16
TCDn_DADDR = 0x2000
TCDn_DOFF = 4
TCDn_ATTR[DSIZE] = 2
TCDn_DLAST_SGA= –16
TCDn_CSR[INT_MAJ] = 1
TCDn_CSR[START] = 1 (Should be written last after all other fields have been initialized)
All other TCDn fields = 0
This generates the following event sequence:
1. User write to the TCDn_CSR[START] bit requests channel service.
2. The channel is selected by arbitration for servicing.
3. eDMA engine writes: TCDn_CSR[DONE] = 0, TCDn_CSR[START] = 0,
TCDn_CSR[ACTIVE] = 1.
4. eDMA engine reads: channel TCD data from local memory to internal register file.
5. The source-to-destination transfers are executed as follows:
a. Read byte from location 0x1000, read byte from location 0x1001, read byte from
0x1002, read byte from 0x1003.
b. Write 32-bits to location 0x2000 → first iteration of the minor loop.
c. Read byte from location 0x1004, read byte from location 0x1005, read byte from
0x1006, read byte from 0x1007.
d. Write 32-bits to location 0x2004 → second iteration of the minor loop.
e. Read byte from location 0x1008, read byte from location 0x1009, read byte from
0x100A, read byte from 0x100B.
f. Write 32-bits to location 0x2008 → third iteration of the minor loop.
g. Read byte from location 0x100C, read byte from location 0x100D, read byte
from 0x100E, read byte from 0x100F.
h. Write 32-bits to location 0x200C → last iteration of the minor loop → major loop
complete.
Chapter 21 Direct Memory Access Controller (eDMA)
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
Freescale Semiconductor, Inc. 385