| 摘要 |
An electronic digital processor which may be used in a hand-held calculator is implemented in a single MOS/LSI semiconductor chip. The processor includes a ROM for storing instruction codes, a RAM for storing data, an arithmetic unit for performing operations on data under control of micro-instructions or commands, and control circuitry including a decoder for generating the commands in response to the instruction codes. The arithmetic unit is controlled by a group of micro-instructions generated from a certain class of instruction codes, while another class of instruction codes includes fields for constants used in some operations such as "compare contents of accumulator with a constant." The class of instructions for controlling the arithmetic unit is directly coupled to a decoder for generating the microinstructions, while the class containing constants is "faked" or indirectly coupled to the decoder through a converter which changes the instruction codes to resemble the ones which control the arithmetic unit. Some of the bit positions which define the constant may, through conversion, be used to generate microinstructions. This arrangement is more efficient in utilization of space on the chip, for a given instruction set.
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