PICers,
I'm having a bit of trouble seeing how you declare local variables in
macros.

I wrote this LCD programme with MACROs all over the place to avoid
having to call nested subroutines and run into problems with the
2-level nests in the 16C57 & 16F84.
Obviously you can't use labels in a MACRO with countdown loops caus
you genearte a duplicate label error if you invoke it twice.So i used
relative jumps in them and it works OK.

The MPASM guide shows how you declare a local variable wth a fixed
value but is it possible to declare one to take care of the jump
address within a loop? say you wanted a label called "rotate" on the
bsf PORTB line? what to do?
Thanx - Ian

;*********************************************************
; LCD_TX  .. a MACRO to drive the HC44780 LCD in 4-bit
;            mode via a 3-wire interface. Rewritten as a MACRO
;            from subroutine lcdtx4 so as to work around the
;            16C57's 2-level nesting limitation.
;
; NOTE .. can only use RELATIVE jumps in MACROS where a loop
;         is involved. Otherwise a duplicated address error
;         will be generated.
; Data byte must already be in the DATA register when the
; routine is called. Data format ... D7 D6 D5 D4 RS x x x
; Registers needed .. charac
;                     count_10
;                     PORTB.CH =     (character\instrucs)
;                     PORTB.CK =     (SIPO clock)
;                     PORTB.EN =     (LCD Enable)
;This routine shifts a NIBBLE of data into the LCD but does so
;using a BYTE count. DATA must be in the HIGH NIBBLE of the
;charac register.
;************************************************************
LCD_TX MACRO
         IFDEF DEBUG
           movlw  0x02
          ELSE
           movlw  0x08
         ENDIF
         movwf    count_10
         bcf      STATUS,C
         bcf      PORTB,CK
         nop                    ;Rest between bit ops.
         bsf      PORTB,CH    ;***Initialise the data port.
LABEL=rotate in SUBROUTINE?????
         rlf      charac,1      ;Rotate the the data thru CARRY, MSB
first.
         btfss    STATUS,C      ;Data bit = 1?
          bcf     PORTB,CH      ;No  - send a zero
         nop                    ;Rest between bit ops.
         bsf      PORTB,CK      ;Clock the bit thru
         nop
         nop                    ;Rest between bit ops.
         bcf      PORTB,CK
         decfsz   count_10,1    ;Stepped down thru 8 bits?
          goto    $-0x0A        ;No  - RELATIVE jump back to bsf
PORTB,CH
         nop                    ;Rest between bit-ops.
         bsf      PORTB,EN      ;Enable the LCD and
         nop
         nop
         nop                    ;transfer the data.
         bcf      PORTB,EN
         nop
         bcf      PORTB,CH      ;Leave PORTB in a defined state. All
LOW.
         ENDM

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body