Cortex-A8 R2P2.pdf - ARM Information Center

Preface< and > Angle brackets enclose replaceable terms for assembler syntaxwhere they appear in code or code fragments. They appear innormal font in running text. For example:• MRC p15, 0 , , , • The Opcode_2 value selects which register is accessed.Timing diagramsThe figure named Key to timing diagram conventions explains the components used intiming diagrams. Variations, when they occur, have clear labels. You must not assumeany timing information that is not explicit in the diagrams.Shaded bus and signal areas are undefined, so the bus or signal can assume any valuewithin the shaded area at that time. The actual level is unimportant and does not affectnormal operation.ClockHIGH to LOWTransientHIGH/LOW to HIGHBus stableBus to high impedanceBus changeHigh impedance to stable busKey to timing diagram conventionsSignalsThe signal conventions are:Signal levelLower-case nPrefix APrefix BThe level of an asserted signal depends on whether the signal isactive-HIGH or active-LOW. Asserted means HIGH foractive-HIGH signals and LOW for active-LOW signals.Denotes an active-LOW signalDenotes Advanced eXtensible Interface (AXI) global and addresschannel signals.Denotes AXI write response channel signals.ARM DDI 0344E Copyright © 2006-2008 ARM Limited. All rights reserved. xxxi