NXP Semiconductors MPC5566 - Page 412

Enhanced Direct Memory Access (eDMA)
MPC5566 Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor 9-51
When the major loop is exhausted, only the major loop channel link fields are used to determine whether
to make a channel link. For example, with the initial fields of:
TCD.CITER.E_LINK = 1
TCD.CITER.LINKCH = 0xC
TCD.CITER value = 0x4
TCD.MAJOR.E_LINK = 1
TCD.MAJOR.LINKCH = 0x7
channel linking executes as:
1. Minor loop done -> set channel 12 TCD.START bit
2. Minor loop done -> set channel 12 TCD.START bit
3. Minor loop done -> set channel 12 TCD.START bit
4. Minor loop done, major loop done -> set channel 7 TCD.START bit
When minor loop linking is enabled (TCD.CITER.E_LINK = 1), the TCD.CITER field uses a nine bit
vector to form the current iteration count.
When minor loop linking is disabled (TCD.CITER.E_LINK = 0), the TCD.CITER field uses a 15-bit
vector to form the current iteration count. The bits associated with the TCD.CITER.LINKCH field are
concatenated onto the CITER value to increase the range of the CITER.
NOTE
After configuration, the TCD.CITER.E_LINK bit and the
TCD.BITER.E_LINK bit must be equal or a configuration error is reported.
The CITER and BITER vector widths must be equal to calculate the major
loop, half-way done interrupt point.
Table 9-25 summarizes how a DMA channel can “link” to another DMA channel, i.e, use another
channel’s TCD, at the end of a loop.
Table 9-25. Channel Linking Parameters
Desired Link
Behavior
TCD Control Field Name Description
Link at end of
Minor Loop
citer.e_link Enable channel-to-channel linking on minor loop
completion (current iteration)
citer.linkch Link channel number when linking at end of minor
loop (current iteration)
Link at end of
Major Loop
major.e_link Enable channel-to-channel linking on major loop
completion
major.linkch Link channel number when linking at end of major
loop