STC89LE53RC datasheet(153/165 Pages) STC

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Local Labels

Local labels may be used within a macro using the following format:

%*DEFINE

(macro_name [(parameter_list)])

[LOCAL list_of_local_labels] (macro_body)

For example, the following macro definition

%*DEFINE

(DEC_DPTR)

LOCAL SKIP

(DEC

DPL

;DECREMENT DATA POINTER

MOV

A, DPL

CJNE

A, #0FFH, %SKIP

DEC

DPL

%SKIP:

)

would be called as

%DEC_DPTR

and would be expanded by ASM51 into

DEC

DPL

;DECREMENT DATA POINTER

MOV

A, DPL

CJNE

A, #0FFH, SKIP00

DEC

DPH

SKIP00:

Note that a local label generally will not conflict with the same label used elsewhere in the source program, since

ASM51 appends a numeric code to the local label when the macro is expanded. Furthermore, the next use of the

same local label receives the next numeric code, and so on.

The macro above has a potential "side effect." The accumulator is used as a temporary holding place for

DPL. If the macro is used within a section of code that uses A for another purpose, the value in A would be lost.

This side effect probably represents a bug in the program. The macro definition could guard against this by saving

A on the stack. Here's an alternate definition for the DEC_DPTR macro:

%*DEFINE

(DEC_DPTR)

LOCAL SKIP

(PUSHACC

DEC

DPL

;DECREMENT DATA POINTER

MOV

A, DPL

CJNE

A, #0FFH, %SKIP

DEC

DPH

%SKIP:

POP

ACC

)

Repeat Operations

This is one of several built-in (predefined) macros. The format is

%REPEAT

(expression)

(text)

For example, to fill a block of memory with 100 NOP instructions,

%REPEAT (100)

(NOP

)

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