NXP Semiconductors K22F series, Reference Manual, Page: 500 / 1407

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.
22.5.4.3 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 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 22-9. Modulo example
Transfer Number Address
1 0x12345670
2 0x12345674
3 0x12345678
4 0x1234567C
5 0x12345670
6 0x12345674
22.5.5 Monitoring transfer descriptor status
This section discusses how to monitor eDMA status.
22.5.5.1 Testing for minor loop completion
There are two methods to test for minor loop completion when using software initiated
service requests. The first is to read the TCDn_CITER field and test for a change.
Another method may be extracted from the sequence shown below. The second method is
Initialization/application information
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
500 NXP Semiconductors