Advanced Configuration and Power Interface Specification

ACPI Source Language (ASL)Reference
To convert
from an
object of this
Data Type
To an object
of this Data
Type
This action is performed by the AML Interpreter:
String Buffer If no buffer object exists, a new buffer object is created. If a buffer object
already exists, it is completely overwritten. If the string is longer than the
buffer, the string is truncated before copying. If the string is shorter than the
buffer, the remaining buffer bytes are set to zero. In either case, the string
is treated as a buffer, with each ASCII string character copied to one buffer
byte, including the null terminator. A null (zero-length) string will be
converted to a zero-length buffer.
Buffer Field The string is treated as a buffer. If this buffer is smaller than the size of the
buffer field, it is zero extended. If the buffer is larger than the size of the
buffer field, the upper bits are truncated.
Compatibility Note: This conversion was first introduced in ACPI 2.0. The
behavior in ACPI 1.0 was undefined.
Debug Object Each string character is displayed as an ASCII character.
Field Unit Each character of the string is written, starting with the first, to the Field
Unit. If the Field Unit is less than eight bits, then the upper bits of each
character are lost. If the Field Unit is greater than eight bits, then the
additional bits are zeroed.
Integer If no integer object exists, a new integer is created. The integer is initialized
to the value zero and the ASCII string is interpreted as a hexadecimal
constant. Each string character is interpreted as a hexadecimal value (‘0’-
‘9’, ‘A’-‘F’, ‘a’-‘f’), starting with the first character as the most significant digit,
and ending with the first non-hexadecimal character, end-of-string, or when
the size of an integer is reached (8 characters for 32-bit integers and 16
characters for 64-bit integers). Note: the first non-hex character terminates
the conversion without error, and a “0x” prefix is not allowed. Conversion of
a null (zero-length) string to an integer is not allowed.
19.3.5.8 Rules for Storing and Copying Objects
The table below lists the actions performed when storing objects to different types of named targets.
ASL provides the following types of “store” operations:
• The Store operator is used to explicitly store an object to a location, with implicit conversion
support of the source object.
• Many of the ASL operators can store their result optionally into an object specified by the last
parameter. In these operators, if the destination is specified, the action is exactly as if a Store
operator had been used to place the result in the destination.
• The CopyObject operator is used to explicitly store a copy of an object to a location, with no
implicit conversion support.
Version 6.0 797