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212 SA-1110 Developer’s Manual
Peripheral Control Module
The value written to the device select (DS[3:0]) field specifies which serial controller device is
serviced by the DMA channel.
The device datum width (DW) field value is fixed for each device type and indicates whether the
device’s data port is one or two bytes wide. If the datum width is programmed incorrectly for a
particular device select, then the results are unpredictable.
The device burst size (BS) field value is fixed for each device type. It indicates how many (four or
eight) beats of the datum width are transferred each time the device requests service. This value is
chosen based on the FIFO size of the particular device. If the burst size is programmed incorrectly
for a particular device select, then the results are unpredictable.
Note: The Big Endian implementation scheme is not supported in the B4 stepping and above.
The device endianess (E) field value indicates the byte ordering within a word when data is read
from or written to memory. If the E bit is zero, then memory is assumed to be little endian. If the bit
is one, then memory is assumed to be big endian. Figure 11-2 shows big and little endian DMA
transfers.
Figure 11-2. Big and Little Endian DMA Transfers
The device data transfer direction (RW) field indicates the direction of the transfer. A zero indicates
the transfer is a write (with respect to the device) and the flow of data will be from memory to the
device. If the RW field is programmed to a one, then the transfer is a read and the flow of data will
A6893-01
D<31>
Half-word wide
Device
Byte-wide
Device
D<0>
DMA
Controller
Big Endian DMA Transfers
3210
32
10
10
3
0
1
2
3
3
2
1
0
To FromFrom To
2
from memory
D<31>
Half-word wide
Device
Byte-wide
Device
D<0>
DMA
Controller
Little Endian DMA Transfers
3210
32
10
32
1
3
2
1
0
0
1
2
3
To FromFrom To
0
from memory