Functional Description
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
17-7
written. The sequence of events to start and complete a chain using single-write start mode is as
follows:
1.
Set the mode register current descriptor start mode bit, MRn[CDSM/SWSM], and the
extended features enable bit MRn[XFE]. Also, clear the channel transfer mode bit,
MRn[CTM]. This initialization indicates basic chaining and single-write start mode.
Also other control parameters may be initialized in the mode register.
2.
Build link descriptor segments in memory.
3.
Poll the channel state (see Table 17-2), to confirm that the specific DMA channel is
idle.
4.
Initialize CLNDARn to point to the first descriptor segment in memory. This write
automatically causes the DMA controller to begin the link descriptor fetch and set
MRn[CS].
5.
SRn[CB] is set by the DMA controller to indicate the DMA transfer is in progress.
6.
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.
17.2.1.1.5 Extended DMA Mode Transfer
The extended DMA mode also operates in chaining and direct mode. It offers additional
capability over the basic mode by supporting striding and a more flexible descriptor structure.
This additional functionality also requires a new and more complex programming model. The
extended DMA mode is activated by setting MRn[XFE].
17.2.1.1.6
Extended Direct Mode
Extended direct mode has the same functionality as basic direct mode with the addition of stride
capabilities. The bit settings are the same as in direct mode with the exception of the MRn[XFE]
being set. Striding on the source address can be accomplished by setting SATRn[SSME] and
setting the desired stride size and distance in SSRn. Striding on the destination address can be
accomplished by setting DATRn[DSME] and setting the desired stride size and distance in
DSRn.
17.2.1.1.7
Extended Direct Single-Write Start Mode
Extended direct single-write start mode has the same functionality as the basic direct single-write
start mode with the addition of stride capabilities. The bit settings are also the same with the
exception of MRn[XFE] being set. Striding on the source address can be accomplished by setting
SATRn[SSME] and setting the desired stride size and distance in SSRn. Striding on the
destination address can be accomplished by setting DATRn[DSME] and setting the desired stride
size and distance in DSRn.
Summary of Contents for MSC8144E
Page 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Page 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Page 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Page 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Page 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Page 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Page 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Page 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Page 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Page 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...