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Defining single bit variables in Microchip C18

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Nemesis77

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bit z charu c18

I want to define flags in my code. In assembler I used to do it as follows:

flags equ 0x020 ; Define variable

#define flag0 flags,0 ; Flag0
#define flag1 flags,1 ; Flag0
etc.

How would I do this in C18. i.e. I want to define a CHAR variable and I want to be able to set or clear each bit of the 8bit CHAR variable. C18 has some predefined for example... INTCONbits.GIE = 1; This statement sets only 1 bit in the INTCON register.
 

c18 bits

You use bitfields.

Code: 
/*--- Relay Structure ---*/

struct RELAYBITS
  {
  unsigned rca:1;     /* SEL_UNBAL relay */
  unsigned earth:1;   /* EARTHSEL relay */
  unsigned ground:1;  /* GND_RLY relay */
  unsigned phase:1;   /* Phase invert relay */
  unsigned bridge:1;  /* Mono amplifier mode */ 
  unsigned dummy:2;   /* Alignment bits */
  unsigned mute:1;    /* MUTE relay */
  };

/*--- Relay bits union ---*/

typedef union
  {
  struct RELAYBITS Bits; 
  unsigned char data;
  }RELAY;
  
volatile RELAY RELAYbits;

You can set and clear the bits like this:

Code: 
RELAYbits.data = 0;  /* Clear all bits */

RELAYbits.Bits.ground = 0;  /* Clear single bit */
RELAYbits.Bits.rca = 1;     /* Set a bit */

Bit fields dont have to be single bits, you could define a bitfield with 3 bits, or any number of bits

Code: 
typedef struct 
  {
  unsigned threebits : 3;
  unsigned twobits : 2;
  }BITS,

volatile BITS Bits;

Bits.threebits = 7;
Bits.twobits = 3;

then you could set them to any value between 0 and the maximum value the bits can hold.
 
microchip c18

Thanx btbass. This is a great answer and even beter than I actualy needed.
 

mcc18 bit field

Look at the Pic18F header files. They make extensive use of bitfields. You can learn a trick or two by studying the header files.
 

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