UM0144 datasheet(14/92 Pages) STMICROELECTRONICS

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3 ST7 Assembler

ST7 Assembler Linker

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UM0144

For example:

The next sections describe the main components of a source code file.

3.3.1

About labels

Label structure

Labels must start in column one. A label may contain up to 30 of any of the following

characters:

●

Upper Case letters (A-Z)

●

Lower case letters (a-z)

●

Digits (0-9)

●

Underscore (_)

The first letter of a label must be a letter or an underscore. Note that upper and lower case are

treated differently because the assembler is case sensitive.

Upon assembly, any label that exceeds 30 characters is truncated and a warning alerts the

user that this has occurred. When truncated, if two of more labels have the same name, a

phase inconsistency error is generated.

When labels are defined, several attributes are defined along with the value.

These are:

●

Size (Byte, Word or Long)

●

Relativity (Linker Relative or Absolute)

●

Scope (Internally or Externally defined)

The function of each attribute is explained in the following sections.

Label size

Defining a label’s size allows the assembler to determine what kind of addressing mode to

choose even if the value associated with the label is undefined.

The default size of the memory location for a label is word (2 bytes). Whenever the label has no

suffix, then the default size is assumed. The directives BYTES, WORDS and LONGS (4

bytes) allow you to change the default.

Regardless of the default size, you can define the size for a specific label by adding a suffix to

it: .b for byte, .w for word and .l for long. The suffix is not used when the label is referred to.

Using of any suffixes other than .b, .w and .l will result in an error upon assembly.

examp

A,$ffff

; long addressing mode

comments

operand

opcode

label

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