Datasheet

45
32142D–06/2013
ATUC64/128/256L3/4U
7. Peripheral DMA Controller (PDCA)
Rev: 1.2.3.1
7.1 Features
• Multiple channels
• Generates transfers between memories and peripherals such as USART and SPI
• Two address pointers/counters per channel allowing double buffering
• Performance monitors to measure average and maximum transfer latency
• Optional synchronizing of data transfers with extenal peripheral events
• Ring buffer functionality
7.2 Overview
The Peripheral DMA Controller (PDCA) transfers data between on-chip peripheral modules such
as USART, SPI and memories (those memories may be on- and off-chip memories). Using the
PDCA avoids CPU intervention for data transfers, improving the performance of the microcon-
troller. The PDCA can transfer data from memory to a peripheral or from a peripheral to memory.
The PDCA consists of multiple DMA channels. Each channel has:
• A Peripheral Select Register
• A 32-bit memory pointer
• A 16-bit transfer counter
• A 32-bit memory pointer reload value
• A 16-bit transfer counter reload value
The PDCA communicates with the peripheral modules over a set of handshake interfaces. The
peripheral signals the PDCA when it is ready to receive or transmit data. The PDCA acknowl-
edges the request when the transmission has started.
When a transmit buffer is empty or a receive buffer is full, an optional interrupt request can be
generated.