Handy ANDI Instruction

An assembler uses bit manipulation to put together (to "assemble") the bit patterns of each machine instruction. This is a typical assignment in a systems programming course. Of course, you will likely write your assembler in C and will use its bitwise operators. But they ultimately become the processor's bitwise operations.

The andi instruction does a bitwise AND of two 32-bit patterns. At run time the 16-bit immediate operand is padded on the left with zero bits to make it a 32-bit operand.

andi d,s,const     # register d loaded with
                   # bitwise AND of immediate operand const
                   # and the contents of register $s.
                   # const is a 16-bit pattern, so
                   # 0x0000 ... const ... 0xFFFF

The three operands of the instruction must appear in the correct order, and const must be within the specified range. The immediate operand in the source instruction always specifies sixteen bits although the zeros on the left can be omitted (such as 0x2).