Block Transfer Mode; Summary On The Transfer Modes; Table 15-3: Comparison Of Dma Transfer Modes - NEC V850E/RS1 User Manual

15.5.3 Block transfer mode

In Block transfer mode, once transfer starts, DMA continues the transfer operation without releasing the
bus until the set number of transfers is done and the TC signal is set. No other DMA request is acknowl-
edged during that Block transfer.
After the Block transfer ends, the DMAC releases the bus before another DMA transfer can be acknowl-
edged.
Figure 15-17 is an example of a Block transfer when two DMA forwarding demands of DMMRQ0 and
DMMRQ3 are generated. The transfer counter for both channels is set to 4 transfers.
DMMRQ0
DMMRQ3
INTDMA0
INTDMA3
Note: The bus is not released

15.5.4 Summary on the transfer modes

Number of elements transferred by each
DMA trigger
Number of triggers required to transfer
DMBCn elements
Bus released after the transfer of a single
element
A higher prioritized DMA request can pre-
empt an ongoing DMA transfer of lower
priority
524
Downloaded from Elcodis.com electronic components distributor
Chapter 15 DMA Functions (DMA Controller)
Figure 15-17: Block Transfer Example (2 Channels)
<2>
<1>
Note
CPU CPU CPU DMA3 DMA3 DMA3
<1> <1> <1>

Table 15-3: Comparison of DMA Transfer Modes

Item
User's Manual U16702EE3V2UD00
DMA3 CPU DMA0 DMA0 DMA0 DMA0
<1> <2> <2> <2>
Single transfer Fixed Channel
mode transfer mode
1 DMBCn elements
DMBCn triggers 1
yes yes
yes no
CPU CPU CPU CPU
<2>
Block transfer mode
DMBCn elements
1
no
no