Functional Description
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
17-9
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.
17.2.1.2 Channel Continue Mode for Cascading Transfer Chains
The channel continue mode (enabled when MRn[CC] is set) offers software the flexibility of
having the DMA controller get started on descriptors that have already been programmed while
software continues to build more descriptors in memory. Software can set the end-of-links
descriptor (EOLND) in basic mode, or end-of-lists descriptor (EOLSD) in extended mode, to
cause the channel to go into a halted state while software continues to build other descriptors in
memory. Software can then set CC to force hardware to continue where it left off. channel
continue is only meaningful for chaining modes, not direct mode.
If CC is set by software while the channel is busy with a transfer, the DMA controller finishes all
transfers until it reaches the EOLND in basic mode or EOLSD in extended mode. The DMA
controller then refetches the last link descriptor in basic mode, or the last list descriptor in
extended mode and clears the channel continue bit. If EOLND or EOLSD is still set for their
respective modes, the DMA controller remains in the idle state. If EOLND or EOLSD is not set,
the DMA controller continues the transfer by refetching the new descriptor.
If CC is set by software while the channel is not busy with a transfer, the DMA controller
refetches the last link descriptor in basic mode, or the last list descriptor in extended mode and
clears the channel continue bit. If EOLND or EOLSD is still set for their respective modes, the
DMA controller remains in the idle state. If the EOLND or EOLSD bits are not set, the DMA
controller continues the transfer by refetching the new descriptor.
17.2.1.2.1 Basic Mode
On a channel continue, the descriptor at the current link descriptor address register (CLNDARn)
is refetched to get the next link descriptor address field as updated by software. The channel halts
if NLNDARn[EOLND] is still set. If EOLND is zero, the next link descriptor address is copied
into CLNDARn and the channel continues with another descriptor fetch of the current link
descriptor address. As a result, two link descriptor fetches always exist after channel continue
before starting the first transfer.
17.2.1.2.2 Extended Mode
On a channel continue, the descriptor at the current list descriptor (CLSDARn) address register is
refetched to get the next list descriptor address field as updated by software. The channel halts if
NLSDARn[EOLSD] is still set. If not, the next list descriptor address is copied into the
CLSDARn register and the channel continues with another descriptor fetch of the current list
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 ...