If peripheral interrupts are enabled, then the peripheral interrupt handler receives an interrupt when
the entire transfer is complete.
8.3.4 Configuring a Peripheral for Ping-Pong Receive
This example configures the μDMA controller to continuously receive 8-bit data from a peripheral
into a pair of 64-byte buffers. The peripheral has a receive FIFO with a trigger level of 8. The example
peripheral uses μDMA channel 8.
8.3.4.1 Configure the Channel Attributes
First, configure the channel attributes:
1. Configure bit 8 of the DMA Channel Priority Set (DMAPRIOSET) or DMA Channel Priority
Clear (DMAPRIOCLR) registers to set the channel to High priority or Default priority.
2. Set bit 8 of the DMA Channel Primary Alternate Clear (DMAALTCLR) register to select the
primary channel control structure for this transfer.
3. Set bit 8 of the DMA Channel Useburst Clear (DMAUSEBURSTCLR) register to allow the
μDMA controller to respond to single and burst requests.
4. Set bit 8 of the DMA Channel Request Mask Clear (DMAREQMASKCLR) register to allow
the μDMA controller to recognize requests for this channel.
8.3.4.2 Configure the Channel Control Structure
This example transfers bytes from the peripheral's receive FIFO register into two memory buffers
of 64 bytes each. As data is received, when one buffer is full, the μDMA controller switches to use
the other.
To use Ping-Pong buffering, both primary and alternate channel control structures must be used.
The primary control structure for channel 8 is at offset 0x080 of the channel control table, and the
alternate channel control structure is at offset 0x280. The channel control structures for channel 8
are located at the offsets shown in Table 8-11.
Table 8-11. Primary and Alternate Channel Control Structure Offsets for Channel 8
DescriptionOffset
Channel 8 Primary Source End PointerControl Table Base + 0x080
Channel 8 Primary Destination End PointerControl Table Base + 0x084
Channel 8 Primary Control WordControl Table Base + 0x088
Channel 8 Alternate Source End PointerControl Table Base + 0x280
Channel 8 Alternate Destination End PointerControl Table Base + 0x284
Channel 8 Alternate Control WordControl Table Base + 0x288
Configure the Source and Destination
The source and destination end pointers must be set to the last address for the transfer (inclusive).
Because the peripheral pointer does not change, it simply points to the peripheral's data register.
Both the primary and alternate sets of pointers must be configured.
1. Program the primary source end pointer at offset 0x080 to the address of the peripheral's receive
buffer.
367July 24, 2012
Texas Instruments-Production Data
Stellaris
®
LM3S6G65 Microcontroller
OBSOLETE: TI has discontinued production of this device.
