Conventions

Conventions that this book can use are described in:

Typographical

The following table describes the typographical conventions:

Table 1. 

StylePurpose
italicIntroduces special terminology, denotes cross-references, and citations.
boldHighlights interface elements, such as menu names. Denotes signal names. Also used for terms in descriptive lists, where appropriate.
monospaceDenotes text that you can enter at the keyboard, such as commands, file and program names, and source code.
monospaceDenotes a permitted abbreviation for a command or option. You can enter the underlined text instead of the full command or option name.
monospace italicDenotes arguments to monospace text where the argument is to be replaced by a specific value.
monospace boldDenotes language keywords when used outside example code.
<and>

Encloses replaceable terms for assembler syntax where they appear in code or code fragments. For example:

MRC p15, 0 <Rd>, <CRn>, <CRm>, <Opcode_2>
small capitalsUsed in body text for a few terms that have specific technical meanings, that are defined in the ARM glossary. For example, implementation defined, implementation specific, unknown, and unpredictable.

Timing diagrams

Figure 1 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.

Figure 1. Key to timing diagram conventions

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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 Figure 1. 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.

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