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IDT DMA Controller
External DMA Operations
79RC32438 User Reference Manual
9 - 18
November 4, 2002
Notes
Figure 9.14 External DMA Operation (Burst Request Mode)
The DMA done (DMADONENx) inputs are GPIO alternate functions (see Chapter 12, General Purpose
I/O Controller) may be asserted by an external peripheral to signal a done event to the DMA controller. As
shown in Figure 9.15, during external peripheral read operations, DMADONENx is sampled on the same
clock edge as the data. As shown in Figure 9.16, during external peripheral write operations, DMADONENx
is sampled on the same clock edge as the byte writes are negated. The DMADONEx inputs are only
sampled in the last data transfer on the memory and peripheral bus of a burst transfer. In other words, if the
specified transfer size results in multiple memory and peripheral bus data transfers, the external peripheral
can only signal a done event during the last data transfer of the burst.
Figure 9.15 Sampling of DMADONENx During External Peripheral Read Transactions
Figure 9.16 Sampling of DMADONENx During External Peripheral Write Transactions
The DMA finished (DMAFINNx) outputs are GPIO alternate functions (See Table 12.1 in Chapter 12,
General Purpose I/O Controller). A DMA finished output is asserted by the DMA controller to signal a
finished event to an external peripheral. During a read transaction, DMAFINNx is asserted for one clock
EXTCLK
DMAREQN
CSNx
Transaction
to Memory
to ExTransaction
to ExTransaction
1
2
3
4
5
1.
2.
DMA requests data transfer by asserting DMAREQNx
The RC32438 acknowledges DMA request by asserting chip select (CSNx) to external DMA peripheral and per-
forming the burst transfer specified in the TS field.
External peripheral reacts to acknowledgment of DMA request by negating DMAREQNx
DMA controller writes data quantity read from external peripheral to memory
DMA controller performs remaining transfers in DMA operation without further DMA requests. A DMA operation
is completed when the byte count reaches zero or DMADONENx is asserted.
3.
4.
5.
EXTCLK
MADDR[25:0]
RWN
CSNx
BWEN[1:0]
OEN
MDATA[15:0]
Address Valid
Data Valid
DMADONENx
DMA Samples DMADONENx
EXTCLK
MADDR[25:0]
RWN
CSNx
BWEN[1:0]
OEN
MDATA[15:0]
Address Valid
Data Valid
DMADONENx
DMA Samples DMADONENx