MSC8144E Reference Manual, Rev. 3
17-8
Freescale
Semiconductor
RapidIO Interface Dedicated DMA Controller
17.2.1.1.8
Extended Chaining Mode
In extended chaining mode, the software must first build list and link descriptor segments in
memory. Then CLSDARn must be initialized to point to the first list descriptor in memory. The
DMA controller loads list descriptors and link descriptors from memory prior to a DMA transfer.
The DMA controller begins the transfer according to the link descriptor information loaded.
Once the current link descriptor is finished, the DMA controller reads the next link descriptor
from memory and begins another DMA transfer. If the current link descriptor is the last in the
list, the DMA controller reads the next list descriptor in memory. The transfer is finished if the
current link descriptor is the last one in the last list in memory or if an error condition occurs. The
sequence of events to start and complete a transfer in extended chaining mode is as follows:
1.
Build link and list descriptor segments in memory.
2.
Poll the channel state (see Table 17-2), to confirm that the specific DMA channel is
idle.
3.
Initialize CLSDARn to point to the first list descriptor in memory.
4.
Clear the mode register channel transfer mode bit, MRn[CTM], to indicate chaining
mode. MRn[XFE] must be set to indicate extended DMA mode. Other control
parameters may also be initialized in the mode register.
5.
Clear, then set the mode register channel start bit, MRn[CS], to start the DMA transfer.
6.
SRn[CB] is set by the DMA controller to indicate the DMA transfer is in progress.
7.
SRn[CB] is automatically cleared by the DMA controller after finishing the transfer of
the last descriptor segment, or if the transfer is aborted (MRn[CA] transitions from a 0
to 1), or if an error occurs during any of the transfers.
17.2.1.1.9
Extended Chaining Single-Write Start Mode
In the extended mode, the single-write start feature allows a chain to be started by writing the
current list descriptor pointer. Setting MRn[CDSM/SWSM] causes MRn[CS] to be set
automatically when CLSDARn is written. The sequence of events to start and complete an
extended chain using single-write start mode is as follows:
1.
Set MRn[CDSM/SWSM], MRn[CTM], and MRn[XFE] to indicate extended chaining
and single-write start mode. Also other control parameters may be initialized in the
mode register.
2.
Build list and link descriptor segments in local memory.
3.
Poll the channel state (see Table 17-2), to confirm that the specific DMA channel is
idle.
4.
Initialize the current list descriptor address register to point to the first list descriptor
segment in memory. This write automatically causes the DMA controller to begin the
list descriptor fetch and set MRn[CS].
Содержание MSC8144E
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Страница 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Страница 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Страница 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Страница 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
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