Panasonic MN1030 User Manual

Chapter 9  Writing Machine Language Instructions and Directive Statements

Writing Directive Statements  171

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