• State Not Answered
  • Locked Locked
  • Replies 9 replies
  • Subscribers 21 subscribers
  • Views 1699 views
  • Users 0 members are here
2025 survey

We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.

Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Accesing bit addressable variables

Elliot Chisholm

I was wondering what the "best" way to set a bit in a variable declared in the bit addressable area.

Originally I declared each bit as an sbit and therefore can set and clear them as follows

uint8_t bdata status ;
sbit enable = staus ^ 0 ;

enable = 1 ;
enable = 0 ;
I think it looks clearer to do as follows
#define ENABLE 0x01

uint8_t bdata status ;

status |= ENABLE ;
status &= ~ENABLE ;

but I am worried that this could less maintainable because there will be many #defines with the same values but related to different variables and confusion could ensue.

I was wondering what other people do and if there is a standard method for doing this?

Parents
  • 0 in reply to Graham Cole

    It looks like mine does. Maybe it has something to do with the way i have defined the variable.

    $NOMACRO
$SEGMENTED CASE MOD167
;
; 'main.SRC' GENERATED FROM INPUT FILE 'main.c'
; COMPILER INVOKED BY:
;	C:\Keil\C166\BIN\C166.EXE main.c BROWSE MOD167 DEBUG
;
$MODINF (43)
		 NAME MAIN

          NCODE  CGROUP  ?PR?MAIN
          SDATA  DGROUP  ?BD0?MAIN,SYSTEM

                 ASSUME  DPP3 : SDATA

      ?BD0?MAIN  SECTION  DATA BITADDRESSABLE 'BDATA0'
         status  DSB  1
         PUBLIC  status
      ?BD0?MAIN  ENDS

          EXTRN  ?C_STARTUP : NEAR
         enable  BIT   status.0
         PUBLIC  enable


                 REGDEF   R0 - R15


       ?PR?MAIN  SECTION  CODE WORD 'NCODE'
; line 1: #include "types.h"
; line 2:
; line 3: #define ENABLE 0x01
; line 4:
; line 5: uint8_t bdata status ;
; line 6:
; line 7: sbit enable = status ^ 0 ;
; line 8:
; line 9: #pragma SRC
; line 10:
; line 11: void main ( void )

	main  PROC  NEAR
	GLOBAL  main
; FUNCTION main (BEGIN  RMASK = @0x8000)
; line 12: {
; line 13:
; line 14:
; line 15:
; line 16: 	enable = 1 ;
	BSET	enable
; line 17: 	enable = 0 ;
	BCLR	enable
; line 18:
; line 19: 	status |= ENABLE ;
	BSET	(status).0
; line 20: 	status &= ~ENABLE ;
	BCLR	(status).0
; line 21:
; line 22: 	while(1)
; line 23: 	{
; line 24:
; line 25: 	}
?C0001:
	JMP	cc_UC,?C0001
; FUNCTION main (END    RMASK = @0x8000)
	main  ENDP
       ?PR?MAIN  ENDS


; line 26:
; line 27: }

	END

Reply
  • 0 in reply to Graham Cole

    It looks like mine does. Maybe it has something to do with the way i have defined the variable.

    $NOMACRO
$SEGMENTED CASE MOD167
;
; 'main.SRC' GENERATED FROM INPUT FILE 'main.c'
; COMPILER INVOKED BY:
;	C:\Keil\C166\BIN\C166.EXE main.c BROWSE MOD167 DEBUG
;
$MODINF (43)
		 NAME MAIN

          NCODE  CGROUP  ?PR?MAIN
          SDATA  DGROUP  ?BD0?MAIN,SYSTEM

                 ASSUME  DPP3 : SDATA

      ?BD0?MAIN  SECTION  DATA BITADDRESSABLE 'BDATA0'
         status  DSB  1
         PUBLIC  status
      ?BD0?MAIN  ENDS

          EXTRN  ?C_STARTUP : NEAR
         enable  BIT   status.0
         PUBLIC  enable


                 REGDEF   R0 - R15


       ?PR?MAIN  SECTION  CODE WORD 'NCODE'
; line 1: #include "types.h"
; line 2:
; line 3: #define ENABLE 0x01
; line 4:
; line 5: uint8_t bdata status ;
; line 6:
; line 7: sbit enable = status ^ 0 ;
; line 8:
; line 9: #pragma SRC
; line 10:
; line 11: void main ( void )

	main  PROC  NEAR
	GLOBAL  main
; FUNCTION main (BEGIN  RMASK = @0x8000)
; line 12: {
; line 13:
; line 14:
; line 15:
; line 16: 	enable = 1 ;
	BSET	enable
; line 17: 	enable = 0 ;
	BCLR	enable
; line 18:
; line 19: 	status |= ENABLE ;
	BSET	(status).0
; line 20: 	status &= ~ENABLE ;
	BCLR	(status).0
; line 21:
; line 22: 	while(1)
; line 23: 	{
; line 24:
; line 25: 	}
?C0001:
	JMP	cc_UC,?C0001
; FUNCTION main (END    RMASK = @0x8000)
	main  ENDP
       ?PR?MAIN  ENDS


; line 26:
; line 27: }

	END

Children