arm 初始化代码中的{CONFIG}语句疑问

ARM9 SC2440和2410得初始化代码中有下面一个定义:

GBLL THUMBCODE
[ {CONFIG} = 16
THUMBCODE SETL {TRUE}
CODE32
|
THUMBCODE SETL {FALSE}
]
网上的朋友有问下面问题的，我也有疑惑，从ARM官方网站查到了答案。特此列出。

请问代码里的 {CONFIG} 代表什么含义，如何知道它是不是等于为16
是某处定义的某个变量？
还是编译的时候某个配置选项？

用{}括起来代表什么含义
CONFIG 是ADS1.2编译器内建变量，还有其他一些内建变量。

Built-in variables and constants

Table 3.3 lists the built-in variables defined by the ARM assembler.

Table 3.3. Built-in variables
{ARCHITECTURE}
Holds the name of the ARM architecture selected by the --device option.

{AREANAME}
Holds the name of the current AREA.

{ARMASM_VERSION}
Holds an integer that increases with each version of armasm.

|ads$version|
Has the same value as {ARMASM_VERSION}.

{CODESIZE}
Is a synonym for {CONFIG}.

{COMMANDLINE}
Holds the contents of the command line.

{CONFIG}
Has the value 32 if the assembler is assembling ARM code, or 16 if it is assembling Thumb code.

{CPU}
Holds the name of the CPU selected by the --device option.

{ENDIAN}
Has the value “big” if the assembler is in big-endian mode, or “little” if it is in little-endian mode. The default value is selected by the --device option.

{FPU}
Holds the name of the FPU. The default FPU name is selected by the --device option.

{INPUTFILE}
Holds the name of the current source file.

{INTER}
Has the boolean value True if /inter is set. The default is False.

{LINENUM}
Holds an integer indicating the line number in the current source file.

{OPT}
Value of the currently-set listing option. The OPT directive can be used to save the current listing option, force a change in it, or restore its original value.

{PC} or .
Address of current instruction.

{PCSTOREOFFSET}
Is the offset between the address of the STR pc,[…] or STM Rb,{…, pc} instruction and the value of pc stored out. This varies depending on the device specified.

{ROPI}
Has the boolean value True if /ropi is set. The default is False.

{RWPI}
Has the boolean value True if /rwpi is set. The default is False.

{VAR} or @
Current value of the storage area location counter.

Built-in variables cannot be set using the SETA, SETL, or SETS directives. They can be used in expressions or conditions, for example:

IF {ARCHITECTURE} = "4T"

The built-in variable |ads$version| must be all in lowercase. The names of the other built-in variables can be in uppercase, lowercase, or mixed. For example:

IF {CpU} = "ARM7TDMI"

Note

All built-in string variables contain case-sensitive values. See CPU names for valid values for {CPU} and {ARCHITECTURE}. See FPU names for valid values for {FPU}. Relational operations on these built-in variables will not match with strings that contain an incorrect case.

Table 3.4 lists the built-in Boolean constants defined by the ARM assembler.

Table 3.4. Built-in Boolean constants
{FALSE}
Logical constant false.

{TRUE}
Logical constant true.

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