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TMS320VC5416
Fixed-Point Digital Signal Processor
SPRS095O – MARCH 1999 – REVISED JANUARY 2005
3.12
DMA Controller
The device direct memory access (DMA) controller transfers data between points in the memory map
without intervention by the CPU. The DMA allows movements of data to and from internal program/data
memory, internal peripherals (such as the McBSPs), or external memory devices to occur in the
background of CPU operation. The DMA has six independent programmable channels, allowing six
different contexts for DMA operation.
3.12.1
Features
The DMA has the following features:
•
The DMA operates independently of the CPU.
•
The DMA has six channels. The DMA can keep track of the contexts of six independent block
transfers.
•
The DMA has higher priority than the CPU for both internal and external accesses.
•
Each channel has independently programmable priorities.
•
Each channel's source and destination address registers can have configurable indexes through
memory on each read and write transfer, respectively. The address may remain constant, be
post-incremented, be post-decremented, or be adjusted by a programmable value.
•
Each read or write internal transfer may be initialized by selected events.
•
On completion of a half- or entire-block transfer, each DMA channel may send an interrupt to the CPU.
•
The DMA can perform double-word internal transfers (a 32-bit transfer of two 16-bit words).
3.12.2
DMA External Access
The DMA supports external accesses to data, I/O, and extended program memory. These overlay pages
are only visible to the DMA controller. A maximum of two DMA channels can be used for external memory
accesses. The DMA external accesses require a minimum of 8 cycles for external writes and a minimum
of 11 cycles for external reads assuming the XIO02 is in consecutive mode (CONSEC = 1), wait state is
set to two, and CLKOUT is not divided (DIVFCT = 00).
The control of the bus is arbitrated between the CPU and the DMA. While the DMA or CPU is in control of
the external bus, the other will be held-off via wait states until the current transfer is complete. The DMA
takes precedence over XIO requests.
•
Only two channels are available for external accesses. (One for external reads and one for external
writes.)
•
Single-word (16-bit) transfers are supported for external accesses.
•
The DMA does not support transfers from the peripherals to external memory.
•
The DMA does not support transfers from external memory to the peripherals.
•
The DMA does not support external-to-external accesses.
•
The DMA does not support synchronized external accesses.
15
AUTOINIT
7
DMS
14
DINM
6
13
IMOD
5
DLAXS
12
CTMOD
4
DIND
11
SLAXS
10
SIND
2
1
DMD
0
8
LEGEND:
R = Read, W = Write,
n
= value present after reset
Figure 3-16. DMA Transfer Mode Control Register (DMMCRn)
Functional Overview
37
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