Datasheet

Introduction
28 Datasheet, Volume 2
1.3 Register Terminology
The bits in configuration register descriptions will have an assigned attribute from
Table 1-3. Bits without a Sticky attribute are set to their default value by a hard reset.
Note: Table 1-3 is a comprehensive list of all possible attributes and included for
completeness.
Intel
®
64 and IA-32 Architectures Software Developer's Manuals
• Volume 1: Basic Architecture
• Volume 2A: Instruction Set Reference, A-M
• Volume 2B: Instruction Set Reference, N-Z
• Volume 3A: System Programming Guide
• Volume 3B: System Programming Guide
Intel
®
64 and IA-32 Architectures Optimization Reference Manual
http://www.intel.com/
products/processor/
manuals/index.htm
Intel
®
Virtualization Technology Specification for Directed I/O Architecture
Specification
http://download.intel.com/
technology/computing/
vptech/
Intel(r)_VT_for_Direct_IO.p
df
Table 1-2. Processor Documents (Sheet 2 of 2)
Document
Document Number/
Location
Table 1-3. Register Attributes Definitions (Sheet 1 of 2)
Attr Description
RO
Read Only: These bits can only be read by software, writes have no effect. The value of the bits
is determined by the hardware only.
RW Read / Write: These bits can be read and written by software.
RC
Read Clear Variant :These bits can be read by software, and the act of reading them
automatically clears them. HW is responsible for writing these bits, and therefore the -V modifier
is implied.
W1S
Write 1 to Set :Writing a 1 to these bits will set them to 1. Writing 0 will have no effect. Reading
will return indeterminate values and read ports are not requited on the register. These are not
supported by critter, and today is only allowed in the Cbo.
WO
Write Only: These bits can only be written by microcode, reads return indeterminate values.
Microcode that wants to ensure this bit was written must read wherever the side-effect takes
place.
RW-O
Read / Write Once: These bits can be read by software. After reset, these bits can only be
written by software once, after which the bits becomes ‘Read Only’.
RW-L
Read / Write Lock: These bits can be read and written by software. Hardware can make these
bits ‘Read Only’ using a separate configuration bit or other logic.
RW1C
Read / Write 1 to Clear: These bits can be read and cleared by software. Writing a ‘1’ to a bit
clears it, while writing a ‘0’ to a bit has no effect.
ROS
RO Sticky: These bits can only be read by software, writes have no effect. The value of the bits
is determined by the hardware only. These bits are only re-initialized to their default value by a
PWRGOOD reset.
RW1S
Read, Write 1 to Set: These bits can be read. Writing a 1 to a given bit will set it to 1. Writing
a 0 to a given bit will have no effect. It is not possible for software to set a bit to "0". The 1->0
transition can only be performed by hardware. These registers are implicitly -V.
RWS
R / W Sticky: These bits can be read and written by software. These bits are only re-initialized
to their default value by a PWRGOOD reset.
RW1CS
R / W1C Sticky: These bits can be read and cleared by software. Writing a ‘1’ to a bit clears it,
while writing a ‘0’ to a bit has no effect. These bits are only re-initialized to their default value by
a PWRGOOD reset.