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

AHB-Lite OverviewA.1.1SpecificationThe AHB-Lite specification differs from the full AHB specification in the followingways:• It is a single-master system. There is only one source of address, control, andwrite data, so no master-to-slave multiplexor is required.• There is no arbitration. The AHB-Lite master always has control of the bus.• There is no master HBUSREQ output. If such an output exists on a master, it isleft unconnected.• There is no master HGRANT input. If such an input exists on a master, it is tiedHIGH.• There is no SPLIT or RETRY slave responses. The AHB-Lite master deals onlywith a slave ERROR response.• The AHB-Lite lock signal HMASTLOCK, compared with HLOCK for fullAHB, and it has the same timing as the address bus and other control signals. If amaster has an HLOCK output, it can be retimed to generate HMASTLOCK.• The AHB-Lite lock signal, HMASTLOCK, must remain stable throughout aburst of transfers, in the same way that other control signals must remain constantthroughout a burst.Using the AHB-Lite interface makes the bus transfers generated by the AHB-Lite filereader easier to understand and easier to debug. Because the AHB-Lite is a singlemaster protocol, an AHB-Lite master always has control of the bus. Unlike AHB,AHB-Lite has no request phase. Consequently, the AHB-Lite bus might be subject towait states during the request phase of the AHB bus.A.1.2CompatibilityTable A-1 on page A-4 lists how masters and slaves designed for use in either full AHBor AHB-Lite can be used interchangeably in different systems.ARM DDI 0243C Copyright © 2003, 2007 ARM Limited. All rights reserved. A-3