THE MACRO-2


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A MACRO is identical to a sub-routine. In fact it is a sub-routine. All the timing associated with a normal sub-routine applies to a Macro.
A Macro is generally a short routine that is called from different places in your program. There is no advantage in producing a MACRO rather than a "sub-routine."
The terminology is simply to make programming more complex.
There is no need to create MACROS, but if you do, here are the requirements.
A Macro can be a Delay routine or a routine that sends out a pulse on a particular line or any other operation - there is no limit to the things it can do.
We have already explained how to produce a sub-routine such as Delay.
Here is the code for Delay as a sub-routine and as a Macro:

  Delay as a sub-routine:

Del1




Main
 NOP
DECFSZ 20h,1
GOTO Del1
RETURN

BSF 06,3
CALL Del1
BCF 06,3
 CALL Del1
GOTO Main		 ;Create delay




;Turn on output line

;Turn off output line

Delay as a MACRO:

Del1

Label



 Main
 MACRO
LOCAL Label
 DECFSZ 20h,1
GOTO Label
ENDM

 BSF 06,3
Del1
BCF 06,3
Del1
GOTO Main		 ;Create delay





;Turn on output line

;Turn off output line
 

In the program above, the word Del1 in Main, is converted to a CALL instruction by the assembler and the micro goes to the address where Del1 Macro is located, when it executes the program. The assembler also converts the instructions at Del1 to three lines of code. The instructions: DECFSZ 20h,1   GOTO Label   ENDM are converted to: DECFSZ 20h,1  GOTO Label   and   RETURN.

The instruction:   LOCAL needs to be explained. In the example below, the word LOCAL refers to a label called Label. The next example uses a label called Findus and Quell. We have used the words Findus and Quell to make the explanation easier to understand.
The instruction LOCAL in a Macro means the next word will be used as a label in the current macro. We have used the word "Quell" in the example below. Normally a label cannot be used twice in a program as the assembler will not know which label to use. But when it is used in a MACRO, the assembler assigns an address within the Macro. This means "Quell" in another Macro will be assembled as a different address.
Although this feature is available, always use a different name for each label.

Del1

 Label



 Del2

 Label


Main
 MACRO
LOCAL Label
 DECFSZ 20h,1
GOTO Label
ENDM

 MACRO
LOCAL Label
DECFSZ 22h,1
GOTO Label
ENDM

 BSF 06,3
Del1
BCF 06,3
Del1
GOTO Main		 ;Create delay











;Turn on output line

;Turn off output line


Del1

Findus



 Del2

Quell


Del3

 Quell

 		 MACRO
LOCAL Findus
 DECFSZ 20h,1
GOTO Findus
ENDM

 MACRO
LOCAL Quell
DECFSZ 22h,1
GOTO Quell
ENDM

 MACRO
LOCAL Quell
DECFSZ 23h,1
GOTO Quell
ENDM		 ;Create delay













 

Since a Macro operates exactly like a sub-routine, you can "go to" another Macro from an existing Macro. Refer to the program below. The instruction "Del1"  is performed as a CALL and the ENDM instruction at the end of the second Macro operates as a RETURN (to Pulse MACRO - in this case).

Pulse



P1







Del1

Delay

 		MACRO
LOCAL P1
MOVLW 03
MOVWF 20h
BSF 06,3
Del1
BCF 06,3
Del1
DECFSZ 20h,1
GOTO P1
 ENDM

MACRO
LOCAL Delay
 DECFSZ 20h,1
GOTO Delay
ENDM		 ;Pulse the output line



;Turn on output line

;Turn off output line
 


To exit from a Macro - use EXITM

 TIMING
Timing (using a 4MHz oscillator):

Del1

Delay



Main

 		MACRO
LOCAL Delay
NOP
NOP
ENDM

BSF 06,3
Del1
BCF 06,3
Del1
GOTO Main

1uS
1uS
1uS

1uS
1uS
1uS
1uS
1uS

NEXT