LM3S5762 Datasheet, PDF (293/841 Pages) Texas Instruments – Stellaris® LM3S5762 Microcontroller

Stellaris® LM3S5762 Microcontroller
transfer is complete. In this case, the alternate control structures are not used and therefore only
the first half of the table needs to be allocated in memory. The second half of the control table is
not needed and that memory can be used for something else. If a more complex transfer mode is
used such as ping-pong or scatter-gather, then the alternate control structure is also used and
memory space should be allocated for the entire table.
Any unused memory in the control table may be used by the application. This includes the control
structures for any channels that are unused by the application as well as the unused control word
for each channel.
Table 8-3. Control Structure Memory Map
Offset
0x0
0x10
...
0x1F0
0x200
0x210
...
0x3F0
Channel
0, Primary
1, Primary
...
31, Primary
0, Alternate
1, Alternate
...
31, Alternate
Table 8-4 on page 293 shows an individual control structure entry in the control table. Each entry
has a source and destination end pointer. These pointers point to the ending address of the transfer
and are inclusive. If the source or destination is non-incrementing (as for a peripheral register), then
the pointer should point to the transfer address.
Table 8-4. Channel Control Structure
Offset
0x000
0x004
0x008
0x00C
Description
Source End Pointer
Destination End Pointer
Control Word
Unused
The remaining part of the control structure is the control word. The control word contains the following
fields:
■ Source and destination data sizes
■ Source and destination address increment size
■ Number of transfers before bus arbitration
■ Total number of items to transfer
■ Useburst flag
■ Transfer mode
The control word and each field are described in detail in “μDMA Channel Control
Structure” on page 310. The μDMA controller updates the transfer size and transfer mode fields as
the transfer is performed. At the end of a transfer, the transfer size will indicate 0, and the transfer
November 17, 2011
293
Texas Instruments-Production Data