Preface
ARM DDI 0388I
Copyright © 2008-2012 ARM. All rights reserved.
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ID073015
Non-Confidential
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Denotes language keywords when used outside example code.
< and >
Enclose replaceable terms for assembler syntax where they appear in code
or code fragments. For example:
MRC p15, 0 <Rd>, <CRn>, <CRm>, <Opcode_2>
SMALL
CAPITALS
Applies when the relevant term is used in body text. For example:
IMPLEMENTATION DEFINED, IMPLEMENTATION SPECIFIC,
UNKNOWN, and UNPREDICTABLE.
Timing diagrams
Key to timing diagram conventions
explains the components used in timing
diagrams. Variations, when they occur, have clear labels. You must not assume any timing
information that is not explicit in the diagrams.
Shaded bus and signal areas are undefined, so the bus or signal can assume any value within the
shaded area at that time. The actual level is unimportant and does not affect normal operation.
Key to timing diagram conventions
Timing diagrams sometimes show single-bit signals as HIGH and LOW at the same time and
they look similar to the bus change shown in
Key to timing diagram conventions
. If a timing
diagram shows a single-bit signal in this way then its value does not affect the accompanying
description.
Signals
The signal conventions are:
Signal level
The level of an asserted signal depends on whether the signal is
active-HIGH or active-LOW. Asserted means:
•
HIGH for active-HIGH signals
•
LOW for active-LOW signals.
Lower-case n
At the start or end of a signal name denotes an active-LOW signal.
Additional reading
This section lists publications by ARM and by third parties.
See Infocenter,
http://infocenter.arm.com
, for access to ARM documentation.
Clock
HIGH to LOW
Transient
HIGH/LOW to HIGH
Bus stable
Bus to high impedance
Bus change
High impedance to stable bus
