MPC8540 datasheet(1035/1302 Pages) FREESCALE

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RapidIO Message Unit

MPC8540 PowerQUICC III Integrated Host Processor Reference Manual, Rev. 1

Freescale Semiconductor

17-111

17.8.3 Message Unit Modes of Operation

The message unit operates in the following modes:

•

Direct mode—Software is expected to program all the necessary registers for sending an

outbound message.

•

Chaining mode—A transfer descriptor that describes the message information is fetched

from local memory before a message is sent.

17.8.4 RapidIO Messaging Description

This section describes controller operations, formats, interrupts, and response conditions.

17.8.4.1 Data Message Controller

The RapidIO controller supports a data message passing programming model for inter-processor

and inter-device communication. This model enables a producer to send a data message across the

interconnect fabric to a consumer’s message hardware, called a mailbox. The receiving mailbox

controller places the message in a queue located in its memory. A data message may consist of one

or more packets depending on the size of the message. When the entire message has been received,

an interrupt is generated (if enabled) for the processor core to process the message. Data messages

can be queued for transmission in the producer’s memory and the message hardware processes

them sequentially. Messages can also be queued in the consumer’s memory while software

processes them sequentially. Software controls the depth of the circular queue in the producer, or

consumer.

The RapidIO data message controller contains the following features:

•

One inbound mailbox (inbox) structure

•

One outbound mailbox (outbox) structure

•

Support for one active letter in the inbox (letters are assigned and maintained by hardware)

•

Support for up to one letter (0) in the outbox for message unit initiated messages

•

Support for up to 16 segments (packets) per message

•

Support for up to 256 bytes per segment (packet)

•

Chaining and direct mode support for outbound messages

The following sections describe the structure and operation of the outbox and inbox hardware in

the data message controller.

17.8.4.2 Outbox Controller Operation

The outbox controller is responsible for sending messages stored in a circular queue in local

memory. The outbox controller supports two modes of operation: direct and chaining mode. In

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