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b. Write 32-bits to location 0x2010 → first iteration of the minor loop.
c. Read byte from location 0x1014, read byte from location 0x1015, read byte from
0x1016, read byte from 0x1017.
d. Write 32-bits to location 0x2014 → second iteration of the minor loop.
e. Read byte from location 0x1018, read byte from location 0x1019, read byte from
0x101A, read byte from 0x101B.
f. Write 32-bits to location 0x2018 → third iteration of the minor loop.
g. Read byte from location 0x101C, read byte from location 0x101D, read byte
from 0x101E, read byte from 0x101F.
h. Write 32-bits to location 0x201C → last iteration of the minor loop → major loop
complete.
14. eDMA engine writes: TCDn_SADDR = 0x1000, TCDn_DADDR = 0x2000,
TCDn_CITER = 2 (TCDn_BITER).
15. eDMA engine writes: TCDn_CSR[ACTIVE] = 0, TCDn_CSR[DONE] = 1, INT[n] =
1.
16. The channel retires → major loop complete. The eDMA goes idle or services the next
channel.
21.5.4.3 Using the modulo feature
The modulo feature of the eDMA provides the ability to implement a circular data queue
in which the size of the queue is a power of 2. MOD is a 5-bit field for the source and
destination in the TCD, and it specifies which lower address bits increment from their
original value after the address+offset calculation. All upper address bits remain the same
as in the original value. A setting of 0 for this field disables the modulo feature.
The following table shows how the transfer addresses are specified based on the setting
of the MOD field. Here a circular buffer is created where the address wraps to the
original value while the 28 upper address bits (0x1234567x) retain their original value. In
this example the source address is set to 0x12345670, the offset is set to 4 bytes and the
MOD field is set to 4, allowing for a 2
4
byte (16-byte) size queue.
Table 21-297. Modulo example
Transfer Number Address
1 0x12345670
Table continues on the next page...
Initialization/application information
K20 Sub-Family Reference Manual, Rev. 1.1, Dec 2012
462
Preliminary
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