AN3350 datasheet(61/185 Pages) STMICROELECTRONICS

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AN3350

Working with the assembler

Doc ID 018512 Rev 2

61/185

As described in the eTPU Assembler Manual, the elements you can use in operands are:

●

Section 10.3.4: Registers

●

Section 10.3.5: Integer immediate values

Note:

Exact operand format and usage depend on the related instruction.

10.3.4

Registers

names, which means that these names cannot be used as identifier names for labels or

symbols.

Some instructions also mention bit names. Bit values are written as a register and bit

combination (i.e. register[bitNumber]), or better, when given a specific name in the eTPU

Assembler Manual, as a lowercase symbol. To determine exact use, consult the

instruction’s description.

10.3.5

Integer immediate values

Use immediate integer values (in decimal, hexadecimal or binary notation) to describe

absolute and relative addresses and constants that are part of numeric calculations.

In most cases, you can replace an integer constant with a constant arithmetic expression,

using a combination of these operators: +, -, <<, >>, *, /, &, &&, |, ||, !, ~, ==, !=, <, <=,

, >=, and parentheses. Priority and interpretation follows the C language standard. The

assembler stores and manipulates integer constants by using 32-bit signed arithmetic.

10.3.6

Symbols

Symbols are placeholders for integer constants. You can use symbols wherever a single

integer constant is required. Symbol names cannot contain spaces and can consist of

alpha-numeric characters, the underscore character (_), and the decimal character (.).

Symbol names can be up to 128 characters long.

Some symbol names are reserved for special purposes. Currently these include all names

beginning or ending with the underscore character (_) or decimal character (.), as well as

all registers and bit names.

Declare and define symbols to assign them value, scope, size and other attributes.

10.3.7

Defining a symbol

You can assign values to symbols in two ways:

●

Create a label — the value is the offset of the defined label, relative to the beginning of

the section in which the label definition appears

●

Use the ‘.equ symbol, value’ or '.label symbol, value' directives — the

value is explicitly specified in the definition

10.3.8

Scope

A symbol's scope is either local or global. Symbols not otherwise declared are local,

meaning they are defined and used only within the file in which they appear. To use a

symbol outside the file in which it is defined, you must use the .global symbol directive

to declare that symbol as global so it will be visible to code in other files. To allow code in

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