Post by thread:MACROS

G'day piclisters I have just discovered a couple of simple macros that I'd like comments on. But first the problem. I use #define to define my port pins because I don't want to have to remember which port they belong to (plus it is easier!). example: #define SDATA RB,5 This is well and good. The problem arises when I want to manipulate a bit mask based on that pin. The wonderful expression someone came up with: iorlw b'00000001' << pin requires the form of port,pin to work. So, for all these years, I've been mixing the two styles in my code and avoiding port pin bit masks whenever possible. It finally occured to me today that a #define statement already has the information needed to make a bit mask. All it takes is a couple of one line macros as follow: sethi MACRO port,pin iorlw b'00000001' << pin endm setlo MACRO port,pin andlw ~ (b'00000001' << pin) endm Usage is simple: way up near the front of my source: #define POT GPIO,5 (rest of pin definitions) DDR EQU b'00110000' ;default port pin DDR down somewhere in the code: ;generate bit mask for RC timer pin movlw DDR ;set pin to o/p setlo POT tris GPIO . . . movlw DDR ;set pin back to input sethi POT trisi GPIO The nice thing about this is that it doesn't matter what the DDR constant gets changed to - I explicitly set the tris bit for that pin. Comments anyone? I'm not particularily happy with my chosen macro names (sethi and setlo) but thats what I came up with off the top of my head. I've tested this with the DOS version 1.40 of MPASM - it generated the same opcodes as explicit andlw and iorlw statements. dwayne Dwayne Reid <spam_OUTdwaynerTakeThisOuTplanet.eon.net> Trinity Electronics Systems Ltd Edmonton, Alberta, CANADA (403) 489-3199 voice (403) 487-6397 fax

John Orhan <.....PICLISTKILLspam@spam@MITVMA.MIT.EDU> wrote: > How many times can a macro be called. As many times as you like. > Can a macro be called from inside another macro? Yes. > What is the difference between a macro and a subroutine? A subroutine exists at just one place in your PIC's memory; each time you want to use it, you CALL the subroutine from somewhere else in your program. When you define a macro, NOTHING gets stored in your PIC's memory. When you USE the macro, though, a full copy of it is inserted in your program at the point where you used it. An analogy might help... If you're composing a document with text and pictures, you can refer to the pictures two ways: The first way is to have just one copy of the picture, with "See Figure 1" in your text wherever you want the reader to look at the picture. That's a subroutine. The other way is to paste a copy of the picture at each point in the document where you want the reader to see it. That's a macro. Make sense? > If I happen to call a macro from outside the page limits, what will > happen? I'm not sure what you're asking. You don't "call" macros; when you use them, you're just asking the assembler to insert the body of your macro there in your program... So they don't behave any differently than if you simply cut-and-pasted code into your program at that point. -Andy === Andrew Warren - fastfwdKILLspamix.netcom.com === Fast Forward Engineering - San Diego, California === http://www.geocities.com/SiliconValley/2499

John Wrote... > Dear PICsters, > I have a question for someone who can tell me about macros. How many times > can a macro be called. Can a macro be called from inside another macro? What > is the difference between a macro and a subroutine? If I happen to call a > macro from outside the page limits, what will happen? > > > Please advise > > Regards John A Macro is not a PIC command. Its a label for people writing code. In the assembler the Macro is some lines of PIC commands that are given a single name to REPRESENT those lines. When the .asm file is assembled those Macro words are substituted for the lines you originally wrote. The advantage of this is that you dont have to keep writing the same few lines over and over again and it can make more sense to have a descriptive name like GET_A2D. A subroutine is different in that the name(label) of the subroutine is a pointer to the address of where the first byte of the subroutine is stored in the program memory. _____________________________ Lance Allen Technical Officer Uni of Auckland Psych Dept New Zealand http://www.psych.auckland.ac.nz _____________________________

John, A small addition to Andy's excellent description: Subroutines change control flow, MACROs do not. A return cannot be used to exit a MACRO. MACROs don't modify the stack. Dan Andrew Warren wrote: {Quote hidden}> John Orhan <.....PICLISTKILLspam.....MITVMA.MIT.EDU> wrote: > > > How many times can a macro be called. > > As many times as you like. > > > Can a macro be called from inside another macro? > > Yes. > > > What is the difference between a macro and a subroutine? > > A subroutine exists at just one place in your PIC's memory; each > time you want to use it, you CALL the subroutine from somewhere > else in your program. > > When you define a macro, NOTHING gets stored in your PIC's > memory. When you USE the macro, though, a full copy of it is > inserted in your program at the point where you used it. > > An analogy might help... If you're composing a document with > text and pictures, you can refer to the pictures two ways: > > The first way is to have just one copy of the picture, with "See > Figure 1" in your text wherever you want the reader to look at > the picture. That's a subroutine. > > The other way is to paste a copy of the picture at each point in > the document where you want the reader to see it. That's a > macro. > > Make sense? > > > If I happen to call a macro from outside the page limits, what will > > happen? > > I'm not sure what you're asking. You don't "call" macros; when > you use them, you're just asking the assembler to insert the > body of your macro there in your program... So they don't behave > any differently than if you simply cut-and-pasted code into your > program at that point. > > -Andy > > === Andrew Warren - EraseMEfastfwdspam_OUTTakeThisOuTix.netcom.com > === Fast Forward Engineering - San Diego, California > === http://www.geocities.com/SiliconValley/2499 -- Daniel Hart Embedded System Design Engineer NBS Technologies, Inc. (Card Technology Corp.) 70 Eisenhower Drive, Paramus, NJ 07652, USA +1 201 845 7373 x183 dhartspam_OUTnbstech.com

A good example of the use of macros for control structures is Karl Lunts PIC Macros (FOR...NEXT, CASE, REPEAT, POLL, WAIT, etc..) http://www.seanet.com/~karllunt/picmacro.htm And other conditional / program flow code at http://www.piclist.com/../microchip/routines --- James Newton (PICList Admin #3) @spam@jamesnewtonKILLspampiclist.com 1-619-652-0593 PIC/PICList FAQ: http://www.piclist.com or .org {Original Message removed}

John Orhan wrote: > > Hi Andy, > > And many thanks for your help. If I tried to invoke a macro on a PIC from > say ram_bank0 to a place in ram_bank1 memory, ( ram_bank0 and ram_bank1 > being memory pages) would the macro work?? Or would I have to switch memory > pages first? Another explanation to supplement the others: Do not think of a macro as the same way you store a subroutine. A macro initially just sits in your assembler program and is not stored in your PIC memory. When you use a macro in your program, the assembler will replace the macro label with the lines of code that is in the macro itself. Simple example: You write a macro: CNSTM MACRO MOVLW 0X020 MOVWF CONSTANT ENDM This stays in your assembler editor. Later in your program: . . CNSTM ;ask for macro MOVLW 0X039 SUBWF CONSTANT,W . . When you assemble, the assembler will take the lines from your macro, and insert it where the macro label is: . MOVLW 0X020 MOVWF CONSTANT MOVLW 0X039 SUBWF CONSTANT,W . . You don't see it (you only see the label) but this is the way it will be stored in your PIC memory. Hope this helps Quentin