Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
821
Inter-Processor Messaging Unit—Intel
®
81341 and 81342
13.0 Inter-Processor Messaging Unit
This chapter describes the Inter-processor Messaging Unit (IMU). IMU operation
modes, setup, external interface, and implementation are detailed in this chapter.
13.1
Overview
The inter-processor messaging unit provides a method for the two integrated Intel
XScale
®
processor processors in to efficiently communicate.
The hardware provides two communication mechanisms:
• Doorbell Registers
• Circular Queues
The IMUs Circular Queue mechanism consists of eight queues. Four of the queues are
for queueing messages from Processor 0 to Processor 1 while the other four are for
queueing messages from Processor 1 to Processor 0. From the point of view of a
particular processor, there are four Send queues and four Receive queues.
Attention bits are provided that can interrupt a given Intel XScale
®
processor processor
when queue full/empty conditions occur as appropriate.
For both the Doorbell Register and Circular Queue mechanism, the IMU provides a fixed
priority scheme. When multiple Doorbell Control Register bits are set, an interrupt
service routine can use this hardware to process Doorbell or Circular queue mechanism
needs in a fixed priority order.