| 摘要 |
PURPOSE:To execute easily a change, an extension, etc. of an instruction system by providing a register designating field, and a selecting bit for designating which is used, the register designating field in a micro-instruction or the register designating field in a machine language instruction, in the micro-instruction for constituting a microprogram. CONSTITUTION:In a microprocessor of a microprogram controlling system provided with an instruction system consisting of a machine language instruction having a register designating field and a machine language instruction having no said field, a register designating field F3, and a selecting bit SB for designating which is used, the register designating field in a micro-instruction or the register designating field in the machine language instruction are provided in the micro-instruction, and in accordance with the contents of the decoder so that a register selecting signal is generated. Accordingly, in case of changing and adding a macro-instruction having no register designating field, it can be coped with by only rewriting a micro-instruction stored in a micro-ROM. |
