mpc5644a Freescale Semiconductor, Inc, mpc5644a Datasheet - Page 7

• Manufacturer Part Number: mpc5644a
• Description: Mpc5644a Microcontroller Data Sheet
• Manufacturer: Freescale Semiconductor, Inc

1.2.3
The enhanced direct memory access (eDMA) controller is a second-generation module capable of performing complex data
movements via 64 programmable channels, with minimal intervention from the host processor. The hardware
micro-architecture includes a DMA engine which performs source and destination address calculations, and the actual data
movement operations, along with an SRAM-based memory containing the transfer control descriptors (TCD) for the channels.
This implementation is utilized to minimize the overall block size. The eDMA module provides the following features:
1.2.4
The INTC (interrupt controller) provides priority-based preemptive scheduling of interrupt requests, suitable for statically
scheduled hard real-time systems.
For high priority interrupt requests, the time from the assertion of the interrupt request from the peripheral to when the processor
is executing the interrupt service routine (ISR) has been minimized. The INTC provides a unique vector for each interrupt
request source for quick determination of which ISR needs to be executed. It also provides an ample number of priorities so that
lower priority ISRs do not delay the execution of higher priority ISRs. To allow the appropriate priorities for each source of
interrupt request, the priority of each interrupt request is software configurable.
When multiple tasks share a resource, coherent accesses to that resource need to be supported. The INTC supports the priority
ceiling protocol for coherent accesses. By providing a modifiable priority mask, the priority can be raised temporarily so that
all tasks which share the resource cannot preempt each other.
The INTC provides the following features:
This device also includes a non-maskable interrupt (NMI) pin that bypasses the INTC and multiplexing logic.
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All data movement via dual-address transfers: read from source, write to destination
Programmable source and destination addresses, transfer size, plus support for enhanced addressing modes
Transfer control descriptor organized to support two-deep, nested transfer operations
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 continuous transfers
— Peripheral-paced hardware requests (one per channel)
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 termination interrupts optionally enabled
Support for scatter/gather DMA processing
Ability to suspend channel transfers by a higher priority channel
9-bit vector addresses
Unique vector for each interrupt request source
Hardware connection to processor or read from register
Each interrupt source can assigned a specific priority by software
Preemptive prioritized interrupt requests to processor
ISR at a higher priority preempts executing ISRs or tasks at lower priorities
Automatic pushing or popping of preempted priority to or from a LIFO
Ability to modify the ISR or task priority to implement the priority ceiling protocol for accessing shared resources
Low latency—three clocks from receipt of interrupt request from peripheral to interrupt request to processor
eDMA
Interrupt controller
Preliminary—Subject to Change Without Notice
MPC5644A Microcontroller Data Sheet, Rev. 4
Overview
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