TM4C123GH6PM Datasheet, PDF (606/1409 Pages) Texas Instruments – Tiva Microcontroller

Micro Direct Memory Access (μDMA)
9.3.4.4
9.3.4.5
9.3.5
9.4
Enable the μDMA Channel
Now the channel is configured and is ready to start.
1. Enable the channel by setting bit 8 of the DMA Channel Enable Set (DMAENASET) register.
Process Interrupts
The μDMA controller is now configured and enabled for transfer on channel 8. When the peripheral
asserts the μDMA request signal, the μDMA controller makes transfers into buffer A using the primary
channel control structure. When the primary transfer to buffer A is complete, it switches to the
alternate channel control structure and makes transfers into buffer B. At the same time, the primary
channel control word mode field is configured to indicate Stopped, and an interrupt is pending.
When an interrupt is triggered, the interrupt handler must determine which buffer is complete and
process the data or set a flag that the data must be processed by non-interrupt buffer processing
code. Then the next buffer transfer must be set up.
In the interrupt handler:
1. Read the primary channel control word at offset 0x088 and check the XFERMODE field. If the
field is 0, this means buffer A is complete. If buffer A is complete, then:
a. Process the newly received data in buffer A or signal the buffer processing code that buffer
A has data available.
b. Reprogram the primary channel control word at offset 0x88 according to Table
9-12 on page 605.
2. Read the alternate channel control word at offset 0x288 and check the XFERMODE field. If the
field is 0, this means buffer B is complete. If buffer B is complete, then:
a. Process the newly received data in buffer B or signal the buffer processing code that buffer
B has data available.
b. Reprogram the alternate channel control word at offset 0x288 according to Table
9-12 on page 605.
Configuring Channel Assignments
Channel assignments for each μDMA channel can be changed using the DMACHMAPn registers.
Each 4-bit field represents a μDMA channel.
Refer to Table 9-1 on page 587 for channel assignments.
Register Map
Table 9-13 on page 607 lists the μDMA channel control structures and registers. The channel control
structure shows the layout of one entry in the channel control table. The channel control table is
located in system memory, and the location is determined by the application, thus the base address
is n/a (not applicable) and noted as such above the register descriptions. In the table below, the
offset for the channel control structures is the offset from the entry in the channel control table. See
“Channel Configuration” on page 589 and Table 9-3 on page 590 for a description of how the entries
in the channel control table are located in memory. The μDMA register addresses are given as a
hexadecimal increment, relative to the μDMA base address of 0x400F.F000. Note that the μDMA
module clock must be enabled before the registers can be programmed (see page 342). There must
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June 12, 2014
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