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Chapter 16 Enhanced Direct Memory Access (eDMA)
MPC5606BK Microcontroller Reference Manual, Rev. 2
292
Freescale Semiconductor
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 will be
reported. The CITER and BITER vector widths must be equal to calculate
the major loop, halfway done interrupt point.
summarizes how a DMA channel can link to another DMA channel, i.e, use another channel’s
TCD, at the end of a loop.
16.5.8
Dynamic programming
16.5.8.1
Dynamic channel linking
Dynamic channel linking is the process of setting the TCD.major.e_link bit during channel execution. This
bit is read from the TCD local memory at the end of channel execution, thus allowing the user to enable
the feature during channel execution.
Because the user is allowed to change the configuration during execution, a coherency model is needed.
Consider the scenario where the user attempts to execute a dynamic channel link by enabling the
TCD.major.e_link bit at the same time the eDMA engine is retiring the channel. The TCD.major.e_link
would be set in the programmer’s model, but it would be unclear whether the actual link was made before
the channel retired.
The coherency model in
is recommended when executing a dynamic channel link request.
Table 16-23. 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.
Summary of Contents for MPC5605BK
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Page 103: ...MPC5606BK Microcontroller Reference Manual Rev 2 Freescale Semiconductor 103 Clocks and power...
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