Indirect addressing replacing

摘要

The addressing arrangement disclosed enables an indirect addressing instruction to be replaced by a direct addressing instruction which references a virtual address. This allows use of a simplified instruction decoder and more efficient usage of a data register in a microprocessor or microcontroller. Virtual address digits such as OOh in an instruction are recognised by a detecting circuit 50 (e.g. a NOR gate) and indicate the indirect addressing mode. Such recognition causes an effective real address to be developed at 60 from the address code in the instruction and from the content of an indirect address register 80, prior to instruction decoding.