LM3S5C36 Datasheet, PDF (354/1068 Pages) Texas Instruments – Stellaris® LM3S5C36 Microcontroller

Micro Direct Memory Access (μDMA)
8.2.1
Each channel also has a configurable arbitration size. The arbitration size is the number of items
that are transferred in a burst before the μDMA controller rearbitrates for channel priority. Using the
arbitration size, it is possible to control exactly how many items are transferred to or from a peripheral
each time it makes a μDMA service request.
Channel Assignments
μDMA channels 0-31 are assigned to peripherals according to the following table. The DMA Channel
Assignment (DMACHASGN) register (see page 401) can be used to specify the primary or secondary
assignment. If the primary function is not available on this microcontroller, the secondary function
becomes the primary function. If the secondary function is not available, the primary function is the
only option.
Note: Channels noted in the table as "Available for software" may be assigned to peripherals in
the future. However, they are currently available for software use. Channel 30 is dedicated
for software use.
The USB endpoints mapped to μDMA channels 0-3 can be changed with the USBDMASEL
register (see page 866).
Because of the way the μDMA controller interacts with peripherals, the μDMA channel for
the peripheral must be enabled in order for the μDMA controller to be able to read and write
the peripheral registers, even if a different μDMA channel is used to perform the μDMA
transfer. To minimize confusion and chance of software errors, it is best practice to use a
peripheral's μDMA channel for performing all μDMA transfers for that peripheral, even if it
is processor-triggered and using AUTO mode, which could be considered a software transfer.
Note that if the software channel is used, interrupts occur on the dedicated μDMA interrupt
vector. If the peripheral channel is used, then the interrupt occurs on the interrupt vector
for the peripheral.
Table 8-1. μDMA Channel Assignments
μDMA Channel
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Primary Assignment
USB Endpoint 1 Receive
USB Endpoint 1 Transmit
USB Endpoint 2 Receive
USB Endpoint 2 Transmit
USB Endpoint 3 Receive
USB Endpoint 3 Transmit
Available for software
Available for software
UART0 Receive
UART0 Transmit
SSI0 Receive
SSI0 Transmit
Available for software
Available for software
ADC0 Sample Sequencer 0
ADC0 Sample Sequencer 1
ADC0 Sample Sequencer 2
ADC0 Sample Sequencer 3
Secondary Assignment
UART2 Receive
UART2 Transmit
General-Purpose Timer 3A
General-Purpose Timer 3B
General-Purpose Timer 2A
General-Purpose Timer 2B
General-Purpose Timer 2A
General-Purpose Timer 2B
UART1 Receive
UART1 Transmit
SSI1 Receive
SSI1 Transmit
UART2 Receive
UART2 Transmit
General-Purpose Timer 2A
General-Purpose Timer 2B
Available for software
Available for software
354
January 23, 2012
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