MSC8144E Reference Manual, Rev. 3
17-4
Freescale
Semiconductor
RapidIO Interface Dedicated DMA Controller
17.2
Functional Description
This section describes the function of the DMA controller.
17.2.1
DMA Channel Operation
In basic mode, the channel can be programmed in basic direct mode or basic chaining mode. In
extended mode, the channel can be programmed in extended direct mode or extended chaining
mode. Extended mode provides more capabilities, such as extended descriptor chaining, striding
capabilities, and a more flexible descriptor structure.
The DMA controller supports misaligned transfers for both the source and destination addresses.
In order to maximize performance, the source and destination engines align the source and
destination addresses to a 64-byte boundary. The DMA always reads/writes the maximum
number of bytes for a given transfer as described by the capability inputs of the DMA controller
except for globally coherent transactions that use the size of the cache coherence granule as
described by the mode select input. Using 256 bytes over the RapidIO interface reduces packet
overhead that translates to increased bandwidth utilization through the interface.
The DMA controller supports bandwidth control, which prevents a channel from consuming all
the data bandwidth in the controller. Each channel is allowed to consume the bandwidth of the
shared resources as specified by the bandwidth control value. After the channel uses its allotted
bandwidth, the arbiter grants the next channel access to the shared resources. The arbitration is
round robin between the channels. This feature is also used to implement the external control
pause feature. If the external control start and pause are enabled in the MRn, the channel enters a
paused state after transferring the data described in the bandwidth control. External control can
restart the channel from a paused state.
The DMA controller is designed to support RapidIO transaction types, including various priority
level support. The DMA controller offers additional features from previous generations in which
the reads can be mapped to non-coherent (NREAD), or maintenance reads. In addition, the writes
can be mapped to non-coherent (NWRITE, NWRITE_R) writes, messages, and maintenance
writes. The DMA programming model permits software to program each DMA engine
independently to interrupt on completed segment, chain, or error. It also provides the capability
for software to resume the DMA engine from a hardware halted condition by setting the channel
continue bit, MRn[CC]. See Table 17-2 for more complete descriptions of the channel states and
state transitions.
17.2.1.1 Basic DMA Mode Transfer
This mode is primarily included for backward compatibility with existing DMA controllers
which use a simple programming model. This is the default mode out of reset. The different
modes of operation under the basic mode are explained in the following sections.
Summary of Contents for MSC8144E
Page 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Page 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Page 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Page 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Page 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Page 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Page 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Page 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Page 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Page 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...