Method and apparatus for manipulating a carry/borrow bit to numerically adjust and immediate value of an instruction during execution

摘要

Method and apparatus for adjusting the range of a data processor instruction field for a data processor (10). The present invention allows the range of a data processor instruction field to be adjusted without requiring decode of the instruction field and without requiring the instruction field value to be modified. In one embodiment, a data processor (10) uses the value of the carry-in/borrow bit (60) provided to an arithmetic unit (30) to selectively adjust the range of the immediate data operand for certain instructions, such as, for example, add immediate (ADDI) and subtract immediate (SUBI).