Microprogramming
The method and the procedure is understood as microprogramming, switching, computing and control processes in an arithmetic logic unit, in particular a built-in calculator (microcontroller, microprocessor), set below the design level of machine instructions at microinstruction level and settle. As micro- programming the preparation of a micro- instruction set can be understood as a sequence of microinstruction sequences in a way to switch control language. Chance of creating the so-called microcode is emphasized in micro- programming by the term micro- code programming or microcode programming that represents the binary form of the micro- instruction set.
Mikrocodeprogrammierbarkeit with a calculating unit adapted to the presence of a microprogram control station is connected, which is controlled by the clock sequence as the microcode instruction sequence. The possibility of flexible programmable sequence controller microinstructions assumes that in each microinstruction (English Micro Instruction) itself, is included on the next microinstruction to be controlled, a calculation rule for reference, that is addressing.
Typically, a machine language instruction set of a processor in the production is (eg for compatibility reasons ) predefined and can not be changed. The forming the micro machine code instruction set (short microcode ) is housed in a read only memory such as EPROM or ROM inside or outside of the calculator, and is possibly loaded at initialization of the arithmetic unit in the microprogram control unit. For the optimization of circuit processes still ways be provided and made arrangements that a microcode corrected, improved, or can be adapted to circumvent costly redesigns in terms of a microcode fix. In the early days of the microprocessor era, the possibility of a flexible microcode programming was necessary and desirable in order to prevent individual leading to a block redesign implementation errors. With the advances in integration and verification of digital circuits, the aspect of reprogrammability seemed long to lose some time in importance.
Nevertheless, interest in the reprogrammability has experienced a revival in recent years. So microprocessors of Intel from the model Pentium Pro ( P6) in the microcode can be reprogrammed. The known as FDIV bug become miscalculation on part of the Intel Pentium P5 processors, however, could not be remedied by microcode programming, but only by processor sharing. The microcode programming provides the possibility to optimize computation control units by means of microcode updates for specific operating systems.
The procedure for programming the purposes of compilation of the micro commands to a micro-program is called in the English-speaking world as Micro Coding. This programming tools are used, as microassembler (English Micro Assembler) are referred to. With these tools it is possible to manage in an orderly manner microinstruction sequences and to translate them into binary code. The learning software microcode simulator Micro conveys the importance and practical approach to the micro- programming of a virtual butterfly on didactic manner.
The concept was introduced in 1951 by Maurice Wilkes ..