ARM Cortex R4F - Manual (Page 453)

Glossary
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Reserved A field in a control register or instruction format is reserved if the field is to be defined by the
implementation, or produces Unpredictable results if the contents of the field are not zero. These
fields are reserved for use in future extensions of the architecture or are
implementation-specific. All reserved bits not used by the implementation must be written as 0
and are to be read as 0.
Rounding mode The IEEE 754 standard requires all calculations to be performed as if to an infinite precision.
For example, a multiply of two single-precision values must accurately calculate the significand
to twice the number of bits of the significand. To represent this value in the destination
precision, rounding of the significand is often required. The IEEE 754 standard specifies four
rounding modes.
In round-to-nearest mode, the result is rounded at the halfway point, with the tie case rounding
up if it would clear the least significant bit of the significand, making it even.
Round-towards-zero mode chops any bits to the right of the significand, always rounding down,
and is used by the C, C++, and Java languages in integer conversions.
Round-towards-plus-infinity mode and round-towards-minus-infinity mode are used in interval
arithmetic.
Saved Program Status Register (SPSR)
The register that holds the CPSR of the task immediately before the exception occurred that
caused the switch to the current mode.
SBO See Should Be One.
SBZ See Should Be Zero.
Scan chain See Boundary scan chain.
Set See Cache set.
Set-associative cache
In a set-associative cache, lines can only be placed in the cache in locations that correspond to
the modulo division of the memory address by the number of sets. If there are n ways in a cache,
the cache is termed n-way set-associative. The set-associativity can be any number greater than
or equal to 1 and is not restricted to being a power of two.
Short vector operation
An operation involving more than one destination register and perhaps more than one source
register in the generation of the result for each destination.
Should Be One (SBO)
Should be written as 1 (or all 1s for bit fields) by software. Writing a 0 produces Unpredictable
results.
Should Be Zero (SBZ)
Should be written as 0 (or all 0s for bit fields) by software. Writing a 1 produces Unpredictable
results.
Should Be Zero or Preserved (SBZP)
Should be written as 0 (or all 0s for bit fields) by software, or preserved by writing the same
value back that has been previously read from the same field on the same processor.
Significand The component of a binary floating-point number that consists of an explicit or implicit leading
bit to the left of the implied binary point and a fraction field to the right.
SPSR See Saved Program Status Register