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Chapter 18 Enhanced Direct Memory Access (eDMA)
MPC5602P Microcontroller Reference Manual, Rev. 4
382
Freescale Semiconductor
18.3
Features
The eDMA is a highly programmable data transfer engine, which has been optimized to minimize the
required intervention from the host processor. It is intended for use in applications where the data size to
be transferred is statically known, and is
not
defined within the data packet itself. The eDMA module
features:
•
All data movement via dual-address transfers: read from source, write to destination
•
Programmable source, destination addresses, transfer size, plus support for enhanced addressing
modes
•
16-channel implementation performs complex data transfers with minimal intervention from a host
processor
— 32 bytes of data registers, used as temporary storage to support burst transfers
(refer to SSIZE bit)
— Connections to the crossbar switch for bus mastering the data movement
•
Transfer control descriptor (TCD) organized to support two-deep, nested transfer operations
— 32-byte TCD per channel stored in local memory
— An inner data transfer loop defined by a minor byte transfer count
— An outer data transfer loop defined by a major iteration count
•
Channel activation via one of three methods:
— Explicit software initiation
— Initiation via a channel-to-channel linking mechanism for continual transfers
— Peripheral-paced hardware requests (one per channel)
NOTE
For all three methods, one activation per execution of the minor loop is
required.
•
Support for fixed-priority and round-robin channel arbitration
•
Channel completion reported via optional interrupt requests
— One interrupt per channel, optionally asserted at completion of major iteration count
— Error terminations are enabled per channel, and logically summed together to form a single
error interrupt.
•
Support for scatter/gather DMA processing
•
Any channel can be programmed so that it can be suspended by a higher priority channel’s
activation, before completion of a minor loop.
Throughout this chapter,
n
is used to reference the channel number. Additionally, data sizes are defined as
byte (8-bit), halfword (16-bit), word (32-bit) and doubleword (64-bit).