User manual

...the world's most energy friendly microcontrollers
2012-04-24 - Giant Gecko Family - d0053_Rev0.96 50
www.energymicro.com
• Ping-pong (switching between the primary or alternate DMA descriptors, for continuous data flow
to/from peripherals)
• Scatter-gather (using the primary descriptor to configure the alternate descriptor)
• Each channel has a programmable transfer length
• Channels 0 and 1 support looped transfers
• Channel 0 supports 2D copy
• A DMA channel can be triggered by any of several sources:
• Communication modules (USART, UART, LEUART)
• Timers (TIMER)
• Analog modules (DAC, ADC)
• External Bus Interface (EBI)
• Software
• Programmable mapping between channel number and peripherals - any DMA channel can be
triggered by any of the available sources
• Interrupts upon transfer completion
• Data transfer to/from LEUART in EM2 is supported by the DMA, providing extremely low energy
consumption while performing UART communications
8.3 Block Diagram
An overview of the DMA and the modules it interacts with is shown in Figure 8.1 (p. 50) .
Figure 8.1. DMA Block Diagram
Interrupts
APB block
APB
memory
mapped
registers
AHB block
AHB-Lite
master
interface
DMA control block
DMA Core
Cortex-M3
AHB to
APB
bridge
AHB
Configuration
control
DMA data
transfer
Error
Channel
done
Peripheral
Peripheral
Channel
select
REQ/
ACK
Configuration
The DMA Controller consists of four main parts:
• An APB block allowing software to configure the DMA controller
• An AHB block allowing the DMA to read and write the DMA descriptors and the source and destination
data for the DMA transfers
• A DMA control block controlling the operation of the DMA, including request/acknowledge signals for
the connected peripherals