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IDT DMA Controller
Internal DMA Operation
79RC32438 User Reference Manual
9 - 12
November 4, 2002
Notes
DMA [0..9] Control Register
Figure 9.6 DMA [0..9] Control Register (DMA[0..9]C)
RUN
Description:
RUN. This bit is automatically set to a one when a DMA operation begins (i.e., when a value is
written into the DMAxDPTR register). If this bit is set, writing a zero into it halts DMA descriptor
processing. The halting of DMA descriptor processing is acknowledged when the H bit in the
DMAxS register is set. When the RUN bit is cleared, writes should not be performed to the
DMAxDPTR and DMAxNDPTR registers until the H bit is set.
Initial Value:
0x0
Read Value:
Previous value written
Write Effect:
Writing a one has no effect; writing a zero clears the bit if it is set.
R
Description:
Reserved.
This bit performs no function.
Initial Value:
Undefined. Must be set to zero.
Read Value:
NA
Write Effect:
NA
MODE
Description:
DMA Mode.
This field controls the operating mode of external DMA operations. All other DMA
operations ignore this field and use Transfer Request Mode.
0
Auto Request Mode
. In this mode, DMA request events from the selected device are ignored
and the DMA controller automatically generates a continuous request event.
1
Burst Request Mode
. In this mode, a DMA request event from the selected device initiates a
burst transfer (i.e., the transfer automatically progresses until a done or finished event). When
the DMA controller observes a request event, it automatically generates a continuous request
event for the remainder of the DMA operation.
2
Transfer Request Mode
. In this mode, a DMA request event signals that a DMA transfer is
requested. The amount of data moved by the DMA is defined by the DMA transfer size for the
selected device.
3
Reserved
Initial Value:
Undefined
Read Value:
Previous value written
Write Effect:
Modify value
ABORT
DMA[0..9]C
0
31
27
0
R
1
RUN
1
2
MODE
ABORT
1