naming a pin or bit question

hotrodhed120

Member

• May 7, 2007

• #1

I've seen in some code the naming of a bit or pin. Could I get someone to show me the correct way to name a pin or bit in assembly?
Example:

bit 0 of OUTPUT file would be named LED
bit 1 of OUTPUT file would be named RELAY
etc.

pin 0 of PORTA would be SW1
pin 1 of PORTA would be SW2
etc.

Can I do this with Assm.?
I'm confused on how its going to recognize which pin of what file your actually naming.

 

E

eng1

New Member

• May 7, 2007

• #2

Use the EQUate directive.

Code:

LED      EQU 0x00
RELAY    EQU 0x01
;...
OUTPUT   EQU PORTB
;...

Relay_On
         BSF OUTPUT, LED
         ;...

 

hotrodhed120

Member

• May 7, 2007

• #3

so the LED EQU 0x00 just means 0 and is not specific to a certain port or register, correct?

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• May 7, 2007

• #4

hotrodhed120 said:

so the LED EQU 0x00 just means 0 and is not specific to a certain port or register, correct?

Click to expand...

0x00 means hexadecimal zero, although obviously zero is the same in all bases anyway.

 

P

Pommie

Well-Known Member

Most Helpful Member

• May 7, 2007

• #5

I like to use the #define directive to assign pins.

For your example, it would be,

Code:

	#define	LED	PORTB,0
	#define	RELAY	PORTB,1

	#define	SW1	PORTA,0
	#define	SW2	PORTA,1

;turn on LED
	bsf	LED
;test SW1
	btfss	SW1

Personally, I like to indicate that the variable is a bit variable by preceding the name with b_ so, LED would become b_LED. In most projects I use bit variables quite a lot. In a recent project I had the following bit variables.

Code:

	cblock	0x20
Flags
	endc

	#define b_TempCarry	Flags,0
	#define b_NotLower	Flags,1
	#define b_BadNumber	Flags,2
	#define b_BadDate	Flags,3
	#define b_BadTime	Flags,4
	#define b_InDate	Flags,5
	#define b_AbortLoad	Flags,6
	#define b_WritingBuffer	Flags,7

Using the above code makes the code much more readable and hence easier to understand.

Mike.

 

donniedj

Banned

• May 7, 2007

• #6

If you are using MPLAB, use Help -> Topics -> MSASM Assembler. #Define is but one of many assembler directives. No need for them to be mysterious anymore.

 

hotrodhed120

Member

• May 8, 2007

• #7

Thanks, Mike, That is exactly what I needed to know, and Thanks for the example also.

 

hotrodhed120

Member

• May 8, 2007

• #8

I was just checking out the easypic4 that gramo has been talking about on www.mikroe.com and found some great online books on the subject. PIC Microcontrollers seems to be pretty staight forward and easy to reference. And its FREE!! Thanks, guys!