Intel IXP400 Features and Hardware Interface, Access-Layer Components Queue Manager IxQMgr API

Intel® IXP400 Software

Access-Layer Components: Queue Manager (IxQMgr) API

18.3Features and Hardware Interface

Figure 89. AQM Hardware Block

		NPE
Queue	AHB	AHB
Control	Slave
Queue	Config/Status	Flag Bus
Buffer		Int
SRAM	Registers
AHB Queue Manager		Intel XScale® Core
		B2415-02

The IxQMgr provides a low-level interface for configuring the AQM, which contains the physical block of static RAM where all the data structures (queues) for the IxQMgr reside. The AQM provides 64 independent queues in which messages, pointers, and data are contained. Each queue is configurable for buffer and entry size and is allocated a status register for indicating relative fullness.

The AQM maintains these queues as circular buffers in an internal, 8-Kbyte SRAM. Status flags are implemented for each queue. The status flags for the lower 32 queues are transmitted to the NPEs via the flag data bus. Two interrupts — (QM1) one for the lower 32 queues and (QM2) one for the upper 32 queues — are used as queue status interrupts.

The AHB interface provides for complete queue configuration, queue access, queue status access, interrupt configuration, and SRAM access.

IxQMgr provides the following services:

•Configures AQM hardware queues.

Configuration of a queue includes queue size, entry size, watermark levels, and interrupt- source-select flag. IxQMgr checks the validity of the configuration parameters and rejects any configuration request that presents invalid parameters.

•Allows callbacks to be registered for each queue. This is also referred as notification callback.

•Enables and disables notifications for each queue.

•Sets the priority of a callback.

•Provides queue-notification source-flag select.

—For queues 0-31, the notification source is programmable as the assertion or de-assertion of one of four status flags: Empty, Nearly Empty, Nearly Full, and Full.

April 2005	IXP400 Software Version 2.0	Programmer’s Guide
266	Document Number: 252539, Revision: 007