Ameba-D User Manual
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On clock edge T2, the DMAC samples that dma_req[0], dma_single[0], and dma_last[0] are all asserted. This is a request for a single
transaction, which is the last transaction in the block. The dma_last[0] and dma_single[0] signals need only be valid on the same clock cycle
that dma_req is generated.
Similarly, Fig 9-16 shows a single transaction followed by a burst transaction, where the burst transaction is the last transaction in the block.
Fig 9-16 Single transaction followed by burst transaction that terminates block
9.2.7.2
Single Transactions – Peripheral is Flow Controller
When the source peripheral is the flow controller, then it can hardcode dma_single to an inactive level (hardware handshaking). This occurs
when:
block_size_bytes_src/src_burst_size_bytes = integer
(10)
When the destination peripheral is the flow controller, then the destination peripheral can hardcode dma_single to an inactive level (hardware
handshaking). This occurs when:
block_size_bytes_dst/dst_burst_size_bytes = integer
(11)
9.2.8
Setting up Transfers
Transfers are set up by programming fields of the CTLx and CFGx registers for that channel. As shown in Fig 9-4, a single block is made up of
numerous transactions – single and burst – which are in turn composed of AHB transfers. A peripheral requests a transaction through the
handshaking interface to the DMAC. The operation of the handshaking interface is different and depends on what is acting as the flow
controller.
Table 9-4 lists the parameters that are investigated in the following examples. The effects of these parameters on the flow of the block transfer
are highlighted. In addition to the software parameters, it includes the channel FIFO depth, DMAH_CH
x
_FIFO_DEPTH, which is configurable
only in coreConsultant.
Table 9-4 Parameters Used in Transfer Examples
Parameter
Description
DMAH_CH
x
_FIFO_DEPTH
Channel
x
FIFO depth in bytes
CTL
x
.TT_FC
Transfer type and flow control
CTL
x
.BLOCK_TS
Block transfer size
CTL
x
.SRC_TR_WIDTH
Source transfer width
CTL
x
.DST_TR_WIDTH
Destination transfer width
CTL
x
.SRC_MSIZE
Source burst transaction length
CTL
x
.DEST_MSIZE
Destination burst transaction length
CFG
x
.MAX_ABRST
Maximum AMBA burst length
CFG
x
.FIFO_MODE
FIFO mode select
CFG
x
.FCMODE
Flow-control mode
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2019-05-15 10:08:03