User guide

Glossary
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Base register A register specified by a load or store instruction that is used to hold the base value for the
address calculation for the instruction. Depending on the instruction and its addressing mode,
an offset can be added to or subtracted from the base register value to form the address that is
sent to memory.
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 data transfer within a burst. For example, an INCR4 burst
comprises four beats.
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.
Boundary scan chain
A boundary scan chain is made up of serially-connected devices that implement boundary scan
technology using a standard JTAG TAP interface. Each device contains at least one TAP
controller containing shift registers that form the chain connected between TDI and TDO,
through which test data is shifted. Processors can contain several shift registers to enable you to
access selected parts of the device.
Branch folding Branch folding is a technique where the branch instruction is completely removed from the
instruction stream presented to the execution pipeline.
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 AMBA are controlled using signals
to indicate the length of the burst and how the addresses are incremented.
See also Beat.