Abstract: A semiconductor integrated circuit includes a main circuit including a transistor, a pseudo-power supply line connected to a first power supply terminal of the main circuit, a first power supply line connected to the pseudo-power supply line via a first switch, a second power supply line connected to a second power supply terminal of the main circuit, a diode having a first end connected to the pseudo-power supply line and a second end connected to the first power supply line so that a potential difference between the pseudo-power supply line and the second power supply line is reduced in a conductive state, and a second switch having a first end connected to the pseudo-power supply line and a second end connected to the second power supply line.

Abstract: A semiconductor integrated circuit and an electronic information device each of which can detect a fault at one of control signals of tristate gates with a smaller area than conventional ones and without reducing the speed of normal operation, by providing a fault detector using tristate gates.

Abstract: A digital signal processor includes an instruction executer configured to execute instructions. The instruction executer determines a first minimum data of a first data and a second data, in parallel with a determination of a second minimum data of a third data and a fourth data. The instruction executer outputs a processed data including the first minimum data and the second minimum data. A bit length of the first minimum data is equal to n bits in length. A bit length of the second minimum data is equal to n bits in length. A bit length of the processed data is equal to at least 2n bits in length.

Abstract: A digital signal processor includes a functional unit configured to execute instructions. The functional unit determines a first minimum data of a first data and a second data, in parallel with a determination of a second minimum data of a third data and a fourth data. The functional unit outputs processed data including the first minimum data and the second minimum data. Each bit length of the first minimum data and the second minimum data is equal to n bits in length. A bit length of the processed data is equal to 2 n bits in length.

Abstract: A digital signal processor configured to perform a Viterbi algorithm includes an instruction fetching unit that fetches instructions and a decoding unit that decodes the instructions fetched by the instruction fetching unit. The digital signal processor also includes an execution unit that executes the instructions decoded by the decoding unit. The execution unit includes an arithmetic logic unit configured to perform a register—register arithmetic logic operation. The arithmetic logic unit compares a first data with a second data, in parallel with a comparison of a third data with a fourth data, and the execution unit outputs new path metrics. Each of the first data, the second data, the third data, and the fourth data is one of four results obtained by adding one of two path metrics to one of two branch metrics.

Abstract: A digital signal processor includes a functional unit configured to execute instructions. The functional unit determines a first minimum data of a first data and a second data, in parallel with a determination of a second minimum data of a third data and a fourth data. The functional unit outputs processed data including the first minimum data and the second minimum data. Each bit length of the first minimum data and the second minimum data is equal to n bits in length. A bit length of the processed data is equal to 2n bits in length.

Abstract: A digital signal processor capable of performing a Viterbi algorithm is provided. The digital signal processor includes an instruction fetching unit that fetches instructions, a decoding unit that decodes the instructions fetched by the instruction fetching unit; and an execution unit that executes the instructions decoded by the decoding unit. The execution unit includes an arithmetic logic unit configured to perform a register-register arithmetic logic operation. The arithmetic logic unit compares a first data with a second data, in parallel with a comparison of a third data with a fourth data. The first data, the second data, the third data, and the fourth data can each be one of four results obtained by adding one of two path metrics to one of two branch metrics. The execution unit outputs new path metrics.

Abstract: A digital signal processor capable of performing a Viterbi algorithm is provided. The digital signal processor includes an instruction fetching unit that fetches instructions; a decoding unit that decodes the instructions fetched by the instruction fetching unit, and an execution unit that executes the instructions decoded by the decoding unit. The execution unit includes a first comparing unit that compares first data with second data and a second comparing unit that compares third data with fourth data. The first comparing unit and the second comparing unit operate in parallel. Also, the first data, the second data, the third data, and the fourth data can each be one of four results obtained by adding one of two path metrics to one of two branch metrics. The execution unit outputs any two new path metrics in a high order position and a low order position respectively.

Abstract: A digital signal processor capable of performing a Viterbi algorithm is provided. The digital signal processor includes an instruction fetching unit that fetches instructions; a decoding unit that decodes the instructions fetched by the instruction fetching unit, and an execution unit that executes the instructions decoded by the decoding unit. The execution unit includes a first comparing unit that compares first data with second data and a second comparing unit that compares third data with fourth data. The first comparing unit and the second comparing unit operate in parallel. Also, the first data, the second data, the third data, and the fourth data can each be one of four results obtained by adding one of two path metrics to one of two branch metrics. The execution unit outputs any two new path metrics in a high order position and a low order position respectively.

Abstract: A method of operating a digital signal processor is provided. The digital signal processor may be provided as a radio communication mobile station, a radio communication base station apparatus, or a CDMA radio communication system. Each path metric PM1 and PM0 of an old state is added to each branch metric BM1 and BM0 separately. A path metric of a new state N is formed by comparing the value of PM1+BM1 to the value of PM0+BM0. A path metric of a new state N+2k−2 is formed by comparing the value of PM1+BM0 to PM0+BM1.

Abstract: A method of operating a digital signal processor is provided. The digital signal processor may be provided as a radio communication mobile station, a radio communication base station apparatus, or a CDMA radio communication system. Each path metric PM1 and PM0 of an old state is added to each branch metric BM1 and BM0 separately. A path metric of a new state N is formed by comparing the value of PM1+BM1 to the value of PM0+BM0. A path metric of a new state N+2k−2 is formed by comparing the value of PM1+BM0 to PM0+BM1.

Abstract: A plurality of units identified by respective addresses are disposed in a register file. Each of the units has a data register for storing data representative of a result of an arithmetic operation, a register for storing an overflow flag indicating the presence or absence of an occurrence of overflow in the arithmetic operation, and a register for storing a sign flag providing an indication of which one of a positive and a negative saturation value should replace the arithmetic operation result in the presence of an occurrence of overflow in the arithmetic operation. Each of the flags is updated in response to a write signal concerning its corresponding register. If at the moment when a data register is fed a read signal, a corresponding overflow flag is set, then either a positive or a negative saturation value, whichever corresponds to the sign flag, is generated on the input side of an arithmetic unit.

Abstract: Two path metrics (PM0, PM1) are read from path metric storing means 1, and two path metrics (BM0, BM1) are read from branch metric storing means 3. An ACS operation is executed using PM0+MB0 and PM1+BM1 by comparing means 5, adding means 6, comparison result storing means 7, and selecting means 8. In parallel with the ACS operation, an ACS operation is executed using PM0+MB1 and PM1+BM0 by comparing means 9, adding means 10, comparison result storing means 11, and selecting means 12.

Abstract: A plurality of units identified by respective addresses are disposed in a register file. Each of the units has a data register for storing data representative of a result of an arithmetic operation, a register for storing an overflow flag indicating the presence or absence of an occurrence of overflow in the arithmetic operation, and a register for storing a sign flag providing an indication of which one of a positive and a negative saturation value should replace the arithmetic operation result in the presence of an occurrence of overflow in the arithmetic operation. Each of the flags is updated in response to a write signal concerning its corresponding register. If at the moment when a data register is fed a read signal, a corresponding overflow flag is set, then either a positive or a negative saturation value, whichever corresponds to the sign flag, is generated on the input side of an arithmetic unit.

Abstract: A plurality of units identified by respective addresses are disposed in a register file. Each of the units has a data register for storing data representative of a result of an arithmetic operation, a register for storing an overflow flag indicating the presence or absence of an occurrence of overflow in the arithmetic operation, and a register for storing a sign flag providing an indication of which one of a positive and a negative saturation value should replace the arithmetic operation result in the presence of an occurrence of overflow in the arithmetic operation. Each of the flags is updated in response to a write signal concerning its corresponding register. If at the moment when a data register is fed a read signal, a corresponding overflow flag is set, then either a positive or a negative saturation value, whichever corresponds to the sign flag, is generated on the input side of an arithmetic unit.

Abstract: In addition to a register file having four general-purpose registers each for storing data, an arithmetic and logic unit for executing an addition instruction, a subtraction instruction, or the like, and a multiplier unit for executing a multiplication instruction, there are provided a controller and a substitute register for storing only data representing the result of operation performed by the multiplier unit in place of any of the four general-purpose registers in the register file. The controller controls the writing and reading of data in and from the register file and the writing and reading of data in and from the substitute register based on a multiplication tag indicative of the one of the four general-purpose registers in place of which the substitute register stores the data representing the result of multiplication and on a multiplication execute flag indicative of whether the data stored in the substitute register is effective or ineffective.

Abstract: In a binary fixed-point number system in which the most significant bit is a sign bit and the decimal point is between the most significant bit and a bit which is lower by one bit than the most significant bit, the circuit scale for digit place aligning means is reduced and a double-precision multiplication with an excellent efficiency is realized. Products of the high-order word/low-order word of a double-precision multiplicand and the high-order word/low-order word of a double-precision multiplier are obtained by using a single-precision multiplying device. A digit place alignment addition operation is performed on the obtained products to produce a double-precision multiplication result.

Abstract: In a processor employing a delayed branch method, delayed branch control which does not complicate instruction execution sequence and improves the readability of a program on the assembler level is implemented without providing a control bit in an instruction code. The delayed branch control according to the present invention involves the use of a branch-information storing circuit for storing the occurrence or nonoccurrence of a branch in a specified one of a continuous sequence of cycles immediately before a current execute cycle which are equal in number to delay slots in the processor. In executing a delayed branch instruction, when the branch-information storing circuit stores the occurrence of a branch in the specified cycle, a branch is disabled. This prevents instruction execution sequence from being complicated even when individual branch conditions for consecutive delayed branch instructions are satisfied, so that the program on the assembler level is improved in readability.

Abstract: In a processor employing a delayed branch method, delayed branch control which does not complicate instruction execution sequence and improves the readability of a program on the assembler level is implemented without providing a control bit in an instruction code. The delayed branch control according to the present invention involves the use of a branch-information storing circuit for storing the occurrence or nonoccurrence of a branch in a specified one of a continuous sequence of cycles immediately before a current execute cycle which are equal in number to delay slots in the processor. In executing a delayed branch instruction, when the branch-information storing circuit stores the occurrence of a branch in the specified cycle, a branch is disabled. This prevents instruction execution sequence from being complicated even when individual branch conditions for consecutive delayed branch instructions are satisfied, so that the program on the assembler level is improved in readability.

Abstract: An arithmetic processor employs two modes of nonpipeline operation and pipeline operation, and is provided with a redundant binary multiplication part for generating redundant binary multiplied results and a supplementary term, first to third intermediate latches for storing two pairs of partial product added results and the supplementary term, a redundant binary accumulation part for accumulating the results of first to third intermediate latches and a value of an accumulation result latch to store the thus accumulated result into the accumulation result latch, and a redundant binary/binary conversion part for converting into a binary numeral the result of the redundant binary multiplication part or the result of the redundant binary accumulation part. Thereby high-speed operations of multiplication instruction and product-sum operation instruction are achieved.