Bit Fields

Bit fields are two or more adjacent bits in the same register. Bit fields adhere only to the short bit naming convention. For example, the three Least Significant bits of the ADCON2 register contain the ADC Operating Mode Selection bit. The short name for this field is MD and the long name is ADMD. Bit field access is only possible in C programs. The following example demonstrates a C program instruction for setting the ADC to operate in Accumulate mode:

ADCON2bits.MD = 0b001;

Individual bits in a bit field can also be accessed with long and short bit names. Each bit is the field name appended with the number of the bit position within the field. For example, the Most Significant MODE bit has the short bit name MD2 and the long bit name is ADMD2. The following two examples demonstrate assembly program sequences for setting the ADC to operate in Accumulate mode:

CopyMOVLW  ~(1<<MD2 | 1<<MD1)
ANDWF  ADCON2,F
MOVLW  1<<MD0
IORWF  ADCON2,F

CopyBCF    ADCON2,ADMD2
BCF    ADCON2,ADMD1
BSF    ADCON2,ADMD0