XC886/888CLM
Introduction
User’s Manual
1-19
V1.3, 2010-02
Introduction, V 1.1
1.6
Reserved, Undefined and Unimplemented Terminology
In tables where register bit fields are defined, the following conventions are used to
indicate undefined and unimplemented function. Further, types of bits and bit fields are
defined using the abbreviations shown in
1.7
Acronyms
lists the acronyms used in this document.
Table 1-4
Bit Function Terminology
Function of Bits
Description
Unimplemented
Register bit fields named “0” indicate unimplemented functions
with the following behavior.
Reading these bit fields returns 0.
Writing to these bit fields has no effect.
These bit fields are reserved. When writing, software should
always set such bit fields to 0 in order to preserve compatibility
with future products. Setting the bit fields to 1 may lead to
unpredictable results.
Undefined
Certain bit combinations in a bit field can be labeled “Reserved”,
indicating that the behavior of the XC886/888 is undefined for
that combination of bits. Setting the register to undefined bit
combinations may lead to unpredictable results. Such bit
combinations are reserved. When writing, software must always
set such bit fields to legal values as provided in the bit field
description tables.
rw
The bit or bit field can be read and written.
r
The bit or bit field can only be read (read-only).
w
The bit or bit field can only be written (write-only). Reading
always return 0.
h
The bit or bit field can also be modified by hardware (such as a
status bit). This attribute can be combined with ‘rw’ or ‘r’ bits to
‘rwh’ and ‘rh’ bits, respectively.
Table 1-5
Acronyms
Acronym
Description
ADC
Analog-to-Digital Converter
ALU
Arithmetic/Logic Unit
BSL
BootStrap Loader
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