IDT DMA Controller
Examples
79RC32438 User Reference Manual
9 - 20
November 4, 2002
Notes
The DEVCS field is not used during memory to memory DMA operations. Table 9.4 summarizes the
memory to DMA FIFO DMA operations and Table 9.5 summarizes DMA FIFO to memory DMA operations.
Examples
Example 1: DMA operation using one descriptor list
(program DMAxDPTR register)
Set up interrupt controller
Set up descriptor
DMAxNDPTR = 0
DMAxDPTR = starting address of the descriptor list
while (DMA done or finished interrupt is not detected) {
perform DMA descriptor operation
DMA updates descriptor status
TS
Transfer Size.
This field specifies the DMA burst transfer size used to access memory during
memory to memory DMA operations.
0 - Reserved
1 - Reserved
2 - word
3 - 2 words
4 - 4 words
5 - 6 words
6 - 8 words
7 - 16 words
DMA Request Event
DMA FIFO has room for a burst transfer of the size specified by the TS field.
DMA Done Event
DMA done event is never generated.
DMA Terminated Event
DMA terminated event is never generated by the FIFO.
DMA Transfer Size
The DMA controller will attempt to transfer a burst of the size specified in the TS field
from memory to the DMA FIFO. Fewer words will be transferred if the byte count
reaches zero.
Limitations
None. A DMA operation may start and end on any byte boundary and may contain any
number of words.
Table 9.4 Memory to DMA FIFO DMA Operations
DMA Request Event
DMA FIFO contains enough data for a burst transfer of the size specified by the TS
field, or the last word of a DMA operation has been transferred to the FIFO.
DMA Done Event
DMA done event is never generated.
DMA Terminated Event
DMA terminated event is never generated.
DMA Transfer Size
The DMA controller will attempt to transfer a burst of the specified size in the TS field
from the DMA FIFO to memory. Fewer words will be transferred if the byte count
reaches zero, or the last word of a DMA operation has been transferred to the FIFO.
Limitations
None. A DMA operation may start and end on any byte boundary and may contain any
number of words.
Table 9.5 DMA FIFO to Memory DMA Operations