at91sam9263 ATMEL Corporation, at91sam9263 Datasheet - Page 272

• Manufacturer Part Number: at91sam9263
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

only if it does not insert more than 16 wait states. If more than 16 wait states are required, then
the peripheral should use a handshaking interface (the default if the peripheral is not pro-
grammed to be memory) in order to signal when it is ready to accept or supply data.
Channel: Read/write datapath between a source peripheral on one configured AMBA layer and
a destination peripheral on the same or different AMBA layer that occurs through the channel
FIFO. If the source peripheral is not memory, then a source handshaking interface is assigned to
the channel. If the destination peripheral is not memory, then a destination handshaking inter-
face is assigned to the channel. Source and destination handshaking interfaces can be assigned
dynamically by programming the channel registers.
Master interface: DMAC is a master on the AHB bus reading data from the source and writing it
to the destination over the AHB bus.
Slave interface: The AHB interface over which the DMAC is programmed. The slave interface
in practice could be on the same layer as any of the master interfaces or on a separate layer.
Handshaking interface: A set of signal registers that conform to a protocol and handshake
between the DMAC and source or destination peripheral to control the transfer of a single or
burst transaction between them. This interface is used to request, acknowledge, and control a
DMAC transaction. A channel can receive a request through one of three types of handshaking
interface: hardware, software, or peripheral interrupt.
Hardware handshaking interface: Uses hardware signals to control the transfer of a single or
burst transaction between the DMAC and the source or destination peripheral.
Software handshaking interface: Uses software registers to control the transfer of a single or
burst transaction between the DMAC and the source or destination peripheral. No special DMAC
handshaking signals are needed on the I/O of the peripheral. This mode is useful for interfacing
an existing peripheral to the DMAC without modifying it.
Peripheral interrupt handshaking interface: A simple use of the hardware handshaking inter-
face. In this mode, the interrupt line from the peripheral is tied to the dma_req input of the
hardware handshaking interface. Other interface signals are ignored.
Flow controller: The device (either the DMAC or source/destination peripheral) that determines
the length of and terminates a DMA block transfer. If the length of a block is known before
enabling the channel, then the DMAC should be programmed as the flow controller. If the length
of a block is not known prior to enabling the channel, the source or destination peripheral needs
to terminate a block transfer. In this mode, the peripheral is the flow controller.
Flow control mode (DMAC_CFGx.FCMODE): Special mode that only applies when the desti-
nation peripheral is the flow controller. It controls the pre-fetching of data from the source
peripheral.
Transfer hierarchy:
Figure 24-2 on page 273
illustrates the hierarchy between DMAC transfers,
block transfers, transactions (single or burst), and AMBA transfers (single or burst) for non-mem-
ory peripherals.
Figure 24-3 on page 273
shows the transfer hierarchy for memory.
AT91SAM9263 Preliminary
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