Zilog ZUSBOPTS Manual do Utilizador descarregar pdf (Página 272)

100

101

Conditional Assembly UM017105-0511

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Zilog Developer Studio II – ZNEO™

User Manual

If name is specified with the .ENDWITH directive, the name must match that used for the

.WITH directive. The intent is to allow for code readability with some checking by the

assembler.

Examine the following

COMPUTE_PAY routine.

COMPUTE_PAY:

; Enter with pointer to an EMPLOYEE in R2, days in R1

; Return with pay in R0

LD.SB R0,EMPLOYEE.SALARY(R2)

MUL R0,R1

RET

The preceding routine could be written using the .WITH directive as follows:

COMPUTE_PAY:

; Enter with pointer to an EMPLOYEE in R2, days in R1

; Return with pay in R0

.WITH EMPLOYEE

LD.SB R0, SALARY(R2)

MUL R0,R1

RET

.ENDWITH EMPLOYEE

Conditional Assembly

Conditional assembly is used to control the assembly of blocks of code. Entire blocks of

code can be enabled or disabled using conditional assembly directives.

Conditional Assembly Directives

The following conditional assembly directives are allowed:

•

IFDEF

•

IFSAME

•

IFMA

Any symbol used in a conditional directive must be previously defined by an

EQU or VAR

directive. Relational operators can be used in the expression. Relational expressions eval-

uate to 1 if true, and 0 if false.

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