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System DMA
96
Direct Memory Access (DMA) Support
fs = 0 and bs = 1: An entire block is transferred each time a DMA_request is
made. This block can be interleaved on the DMA port with other channel
requests.
fs = 0 and bs = 0: An element is transferred each time a DMA_request is
made. This element can be interleaved on the DMA port with other chan-
nel requests.
fs = 1 and bs = 1: This is not allowed and causes undefined results.
PRIO: Channel priority
-
Prio = 1: The logical channel has the highest priority level.
Prio = 0: The logical channel has the lowest priority level.
ENABLE: Logical channel enable
-
This bit is used to enable/disable the transfer in the DMA channel.
Enable = 1: The transfer starts.
Enable = 0: The transfer stops, and it is reset.
This bit is automatically cleared by the DMA hardware once the transfer is
accomplished. Clearing of this bit by the DMA has the priority over write by
the processor. If both occur simultaneously, the configuration write is dis-
carded.
AUTO_INIT: Autoinitialization at the end of the transfer
-
Only supported in OMAP 3.0/1 compatible mode. In OMAP 3.2 mode,
when bit OMAP3_1_COMPATIBLE_DISABLE = 1, this bit must always be
set to 0.
Auto_init = 1: DMA is in autoinitialization mode. Once the current transfer
is complete, the channel automatically reinitializes itself and starts a new
transfer if repeat or end_prog bits is set.
Auto_init = 0: DMA is in non-autoinitialization mode. The DMA channel
stops at the end of the current transfer.
There are two ways to stop a channel while it is in auto-init mode:
Write 0 in DMA_CCR.ENABLE bit: the channel immediately stops.
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Write 0 in DMA_CCR.AUTO-INIT: the channel completes the current
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transfer and stops.
REPEAT: Repetitive operation
-
Only supported in OMAP 3.0/3.1 compatible mode. In OMAP 3.2 mode,
when bit OMAP3_1_Compatible_Disable = 1, this bit must always be set
to 0. The functionality of repeat and end_prog are dependent on each oth-
er. See Table 27, Autoinitialization Configuration Bits Summary, for more
details (following descriptions do not cover all possibilities).
SPRU755B
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