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The 320xx or NS32000 was a series of microprocessors from National Semiconductor. They were likely the first 32-bit general-purpose microprocessors on the market, but due to a number of factors never managed to become a major player. The 320xx series was also used as the basis of the Swordfish microcontroller. It was replaced by the CompactRISC architecture in mid-1990. ==Architecture== |} The processors had 8 general-purpose 32-bit registers, plus a series of special-purpose registers: * Frame pointer * Stack pointer (one each for user and supervisor modes) * Static base register, for referencing global variables * Link base register for dynamically linked modules (object orientation) * Program counter * A typical processor status register, with a low-order user byte and a high-order system byte. (Additional system registers not listed). The instruction set was very much in the CISC model, with 2-operand instructions, memory-to-memory operations, flexible addressing modes, and variable-length byte-aligned instruction encoding. Addressing modes could involve up to two displacements and two memory indirections per operand as well as scaled indexing, making the longest conceivable instruction 23 bytes. The actual number of instructions was much lower than that of contemporary RISC processors. Unlike some other processors, autoincrement of the base register was not provided; the only exception was a "top of stack" addressing mode that would pop sources and push destinations. Uniquely, the size of the displacement was encoded in its most significant bits: 0, 10 and 11 preceded 7-, 14- and 30-bit signed displacements. (Although the processors were otherwise consistently little-endian, displacements in the instruction stream were stored in big-endian order). General-purpose operands were specified using a 5-bit field. To this could be added an index byte (specifying the index register and 5-bit base address), and up to 2 variable-length displacements per operand. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「NS320xx」の詳細全文を読む スポンサード リンク
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