Bit Manipulation


These instructions affect single bits in a byte. All instructions test the bit before affecting it.

BTST Tests a bit
BSET Tests a bit, then sets it (1)
BCLR Tests a bit, then resets it (0)
BCHG Tests a bit, then inverts it (0 -> 1, 1 -> 0)
 

Bit field instructions allow manipulation of bits across a 32 bit field. Bit field instructions were introduced in the 68020 microprocessor and are not supported by the 68000 microprocessor. EASy68K is normally a 68000 only environment but does support a modified form of bit field instructions for educational purposes. In EASy68K the bit field instructions are restricted to using only 68000 addressing modes. An assembler directive or menu option in EASy68K enables or disables the assembly of bit field instructions.

BFCHG Test a bit field, then complement it
BFCLR Test a bit field, then clear it to 0
BFEXTS Test a bit field, then sign extend it to 32 bits and load it into the specified data register
BFEXTU Test a bit field, then zero extend it to 32 bits and load it into the specified data register
BFFFO Test a bit field, then put the bit number of the first bit that contains 1 in the specified data reigster
BFINS Insert the bit field from the specified data register into the destination, then set the condition codes
BFSET Test a bit field, then set it to 1
BFTST Test a bit field