Realtek Ameba-D RTL872 D Series User Manual page 95

The destination peripheral enters the Single Transaction Region when the number of bytes left to complete in the destination block
transfer is less than dst_burst_size_bytes. If:
blk_size_bytes/dst_burst_size_bytes = integer
then the destination never enters this region, and the destination block uses only burst transactions.
Note: The above conditions cause a peripheral to enter the Single Transaction Region. When the peripheral is outside the Single
Transaction Region, then the DMAC responds to only burst transaction requests. Whether the peripheral knows that it is in the Single
Transaction Region or not, it must always generate burst requests outside the Single Transaction Region, or the DMA block transfer stalls.
Once in the Single Transaction Region, the DMAC can complete the block transfer using single transactions.
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Either the source or destination peripheral is the flow controller – The destination or source peripheral enters the Single Transaction
Region when the flow control peripheral–that is, the source or destination – signals the last transaction in the block and when the
amount of data left to be transferred in the destination/source block is less than that which is specified by
dst_burst_size_bytes/src_burst_size_bytes.
9.2.6.2 Early-Terminated Burst Transaction
When a source or destination peripheral is in the Single Transaction Region, a burst transaction can still be requested. However,
src_burst_size_bytes/dst_burst_size_bytes is greater than the number of bytes left to complete in the source/destination block transfer at the
time that the burst transaction is triggered. In this case, the burst transaction is started and "early-terminated" at block completion without
transferring the programmed amount of data – that is, src_burst_size_bytes or dst_burst_size_bytes – but only the amount required to
complete the block transfer. An Early-Terminated Burst Transaction occurs between the DMAC and the peripheral only when the peripheral is
not the flow controller.
9.2.6.3 Hardware Handshaking – Peripheral Is Not Flow Controller
Fig 9-6 illustrates the hardware handshaking interface between a peripheral – whether a destination or source – and the DMAC when the
peripheral is not the flow controller.
User Manual
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Fig 9-6 Hardware handshaking interface
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Direct Memory Access Controller (DMAC)
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