Memory Map / Register Definition; General Operation - NXP Semiconductors freescale KV4 Series Reference Manual

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• Operation at a 1-to-1 clock frequency with the bus masters

• Programmable configuration for fixed-priority or round-robin slave port arbitration

(see the chip-specific information).

20.3 Memory Map / Register Definition

This crossbar switch is designed for minimal gate count. It, therefore, has no memory-

mapped configuration registers.

Please see the chip-specific information for information on whether the arbitration

method in the crossbar switch is programmable, and by which module.

20.4 Functional Description

When a master accesses the crossbar switch, the access is immediately taken. If the

targeted slave port of the access is available, then the access is immediately presented on

the slave port. Single-clock or zero-wait-state accesses are possible through the crossbar.

If the targeted slave port of the access is busy or parked on a different master port, the

requesting master simply sees wait states inserted until the targeted slave port can service

the master's request. The latency in servicing the request depends on each master's

priority level and the responding slave's access time.

Because the crossbar switch appears to be just another slave to the master device, the

master device has no knowledge of whether it actually owns the slave port it is targeting.

While the master does not have control of the slave port it is targeting, it simply waits.

A master is given control of the targeted slave port only after a previous access to a

different slave port completes, regardless of its priority on the newly targeted slave port.

This prevents deadlock from occurring when:

• A higher priority master has:

• An outstanding request to one slave port that has a long response time and

• A pending access to a different slave port, and

• A lower priority master is also making a request to the same slave port as the pending

access of the higher priority master.

Freescale Semiconductor, Inc.

KV4x Reference Manual, Rev. 2, 02/2015

Chapter 20 Crossbar Switch Lite (AXBS-Lite)