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Intel^® EP80579 Integrated Processor
7.1.2
Register Field Access Attributes
Table 7-8 describes the register field access attribute acronyms that this document
uses in its summaries and descriptions.
Table 7-8. Register Field Access Attributes
Attribute
RV
RO
WO
WRC
RC
RW
RWC
RCWC
RW0C
R0/W
RO/RWC
RS/W1C
RWS
RWL
RWO
Description
Reserved – A reserved field.
Read-Only – Software/BIOS can only read this bit. Contents are either hardwired or set by
hardware.
Write-Only – Not supported as a bit. The write causes a hardware event to take place.
Write/Read to Clear – Writes and reads clear. See bit descriptions.
Read to Clear – Cleared automatically when read.
Read/Write – Software/BIOS can read and write this bit.
Read/Write-Clear – Software/BIOS can read this bit and must write to a 1 to clear this bit.
Read-Clear/Write-Clear – Cleared when read or Write one to clear.
Read/Write zero to Clear – Software/BIOS can read this bit, and must write to a 0 to clear this
bit.
Read zero/Write – This register will only read 0. Must read register description for write actions.
Read only/Read-Write-Clear – Attribute dependent on configuration. See bit description
Read-Set/Write-Clear – Read to set, write 1 to clear
Read/Write-Set – Software/BIOS can read this bit and write it to a 1. Hardware clears this bit.
Read/Write-Lock – Software/BIOS can read and write this bit. Hardware or another
configuration bit can lock this bit and prevent it from being updated.
Read/Write-Once – Software/BIOS can read this bit, but can only write this bit once. It is a
special form of RWL. Once any byte within a register with RWO bits has been written, the RWO
bits are locked and only a reset can clear its contents. Any exceptions are clearly documented.
In some cases, the access attribute for a field may depend on a setting of a fuse or a
value in another register. In this case, the access types for the field will be of the form
“X or Y”. Readers should consult the description of the field for additional information
on the conditions that enable the various access types. For example, a field FOO that is
either RO or RW based on the setting of a fuse bit would have an access type of “RO or
RW”.
7.1.3
Register Nomenclature and Values
The summary and description tables also include register and field values. In general, a
number is given by a string of digits followed by a single-character that identifies the
base as decimal, “d”, hexadecimal, “h”, or binary, “b”. Both the digits and base pieces of
a number are always case-insensitive¹. That is, beefh and BEEFH represent the same
hexadecimal number. A value of 0 (zero) does not require a base character. If a value is
non-zero, the default base is assumed to be binary unless stated otherwise. All
hexadecimal and decimal numbers must always have a base character.
In addition to the legal digits for the base, the digit string can contain “x” to denote
undefined values. Typically, Xh is equivalent to XXXXb, XXh is equivalent to
XXXXXXXXb. However, a 5-bit wide field that is undefined can be represented as both
XXh and XXXXXb; that is, a nibble in a hex representation must be “x” if any of its bits
are “x”.
1. The “suggested” convention is that digits are always upper case while the base is always lower case.
August 2009
Order Number: 320066-003US
Intel^® EP80579 Integrated Processor Product Line Datasheet
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