Panasonic MN1030 user manual 14 equ, Label Operation Operand Name Equ Expression

Chapter 9 Writing Machine Language Instructions and Directive Statements

9.4.14 equ

Syntax

label	operation	operand
name	equ	expression

Functional description

This directive defines the name to be the value of the expression coded in the operand. When that name is coded in the operand of machine language instructions or directive instructions, the assembler will reference the name's value.

System constants often used in programs (memory size, clock frequency, etc.) can be assigned to names that describe those values.

MEMORY equ 0x20

MOTOR equ 10

STOP equ 0b00001000

BASE equ 0x1000

This allows numbers used in programs to be coded as descriptive names instead, making programs easier to read. Furthermore, values can be changed just by modifying the equ directive, which in turn changes the data wherever it is used. This makes programs easier to maintain.

Operand coding rules

The expression coded in the operand must result in the attribute abs (absolute). Refer to Section 8.7.4, "Expression Attributes", regarding attributes of expressions.

If the attributes of expressions are not the attribute abs (absolute), #define of the assembler control state- ment should be used, instead of the equ of the directive statement..

Names defined in other programs cannot be specified within expression. Names defined once with the equ directive cannot be defined again.

No memory area is reserved when an equ directive statement is executed.

NOTE:	Symbols with unresolved values cannot be coded in the operand. In the
	following example, the value of ram1 is not resolved at the point where the value
	of ram2 is to be resolved, so the assembler will generate an error.
	Error example:
	ram2	equ	ram1+0x1
	ram1	equ	0x10
	By changing the order such that the value of ram1 is resolved first, no error will
	occur.
	No error example:
	ram1	equ	0x10
	ram2	equ	ram1+0x1

Writing Directive Statements 171