Glossary
D-3
Glossary
data size:
The number of bits (8, 16, or 32) used to represent a particular
number.
decode phase:
The phase of the pipeline in which the instruction is decoded
(identified).
DMA coprocessor:
A peripheral that transfers the contents of memory loca-
tions independently of the processor (except for initialization).
DMA controller:
See DMA coprocessor.
DP:
See data-page pointer.
dual-access RAM:
Memory that can be accessed twice in a single clock
cycle. For example, code that can read from and write to a RAM in one
clock cycle.
E
external interrupt:
A hardware interrupt triggered by a pin.
extended-precision floating-point format:
A 40-bit representation of a
floating-point number with a 32-bit mantissa and an 8-bit exponent.
extended-precision register:
A 40-bit register used primarily for extended-
precision floating-point calculations. Floating-point operations use bits
39–0 of an extended-precision register. Integer operations, however, use
only bits 31–0.
F
FIFO buffer:
First-in, first-out buffer. A portion of memory in which data is
stored and then retrieved in the same order in which it was stored. Thus,
the first word stored in this buffer is retrieved first.
H
hardware interrupt:
An interrupt triggered through physical connections
with on-chip peripherals or external devices.
hit:
A condition in which, when the processor fetches an instruction, the
instruction is available in the cache.