AMBA Design Kit Technical Reference Manual - ARM Information ...

AHB ComponentsNoteWhen connecting to an output port on the Bus Matrix, the HSEL pin must be connectedto the attached slave even if there is only one slave present. If this is not done, the slavemight see spurious transfers under certain circumstances.Locked sequencesThe Bus Matrix is only designed to support locked sequences that target a single outputport. Because of this, a snooping bus across all input ports is not required. This providesarbitration for locked transfers on all layers simultaneously. In addition, the Bus Matrixis not designed to cope with a SPLIT response to a locked transfer. If this occurs, theBus Matrix correctly passes the SPLIT response back to the initiating master, but itmight then enable another master, connected to a different input port, to access theoutput port targeted by the first master.Full AHB and AHB-LiteThe Bus Matrix inherently supports both full AHB and AHB-Lite systems. However,you must take care with SPLIT responses. The Bus Matrix correctly passes back aSPLIT response, but then relies on an arbiter on the AHB layer connected to the relevantinput port to ensure that the initiating master is degranted until unsplit by the slave.3.8.6 Programmer's modelThe design of the Bus Matrix can be divided into input stage, decode stage, and outputstage as described in Block functionality on page 3-27. Figure 3-9 on page 3-27 showsan Bus Matrix design with:• four slave ports, for connection to bus masters• three master ports, for connection to slaves.3-26 Copyright © 2003, 2007 ARM Limited. All rights reserved. ARM DDI 0243C