Glossary

Base register write-back

 

Updating the contents of the base register used in an instruction target address calculation so that

 

the modified address is changed to the next higher or lower sequential address in memory. This

 

means that it is not necessary to fetch the target address for successive instruction transfers and

 

enables faster burst accesses to sequential memory.

Beat

Alternative word for an individual transfer within a burst. For example, an INCR4 burst

 

comprises four beats.

 

See also Burst.

BE-8

Big-endian view of memory in a byte-invariant system.

 

See also BE-32, LE, Byte-invariant and Word-invariant.

BE-32

Big-endian view of memory in a word-invariant system.

 

See also BE-8, LE, Byte-invariant and Word-invariant.

Big-endian

Byte ordering scheme in which bytes of decreasing significance in a data word are stored at

 

increasing addresses in memory.

 

See also Little-endian and Endianness.

Big-endian memory

Memory in which:- a byte or halfword at a word-aligned address is the most significant byte or

 

halfword within the word at that address - a byte at a halfword-aligned address is the most

 

significant byte within the halfword at that address.

 

See also Little-endian memory.

Block address

An address that comprises a tag, an index, and a word field. The tag bits identify the way that

 

contains the matching cache entry for a cache hit. The index bits identify the set being

 

addressed. The word field contains the word address that can be used to identify specific words,

 

halfwords, or bytes within the cache entry.

 

See also Cache terminology diagram on the last page of this glossary.

Branch prediction

The process of predicting if conditional branches are to be taken or not in pipelined processors.

 

Successfully predicting if branches are to be taken enables the processor to prefetch the

 

instructions following a branch before the condition is fully resolved. Branch prediction can be

 

done in software or by using custom hardware. Branch prediction techniques are categorized as

 

static, in which the prediction decision is decided before run time, and dynamic, in which the

 

prediction decision can change during program execution.

Breakpoint

A breakpoint is a mechanism provided by debuggers to identify an instruction at which program

 

execution is to be halted. Breakpoints are inserted by the programmer to enable inspection of

 

register contents, memory locations, variable values at fixed points in the program execution to

 

test that the program is operating correctly. Breakpoints are removed after the program is

 

successfully tested.

 

See also Watchpoint.

Burst

A group of transfers to consecutive addresses. Because the addresses are consecutive, there is

 

no requirement to supply an address for any of the transfers after the first one. This increases

 

the speed at which the group of transfers can occur. Bursts over AHB or AXI buses are

 

controlled using the xBURST signals to specify if transfers are single, four-beat, eight-beat, or

 

16-beat bursts, and to specify how the addresses are incremented.

 

See also Beat.

Byte

An 8-bit data item.

ARM DDI 0363E

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ARM r1p3, R4F manual See also Burst, See also Beat