Method of designing semiconductor integrated circuit device, and apparatus for designing the same
First Claim
1. A method of designing a semiconductor integrated circuit device, which lays out and wires a circuit cell group according to net information, comprising:
- a longest wiring load calculating step for calculating a wiring load of a drivable allowable longest wiring having taken into consideration a waveform rounding, as a first load for each load capacitance driven by the circuit cell;
a wiring load estimating step for calculating an input load capacitance of a next-stage circuit cell and a second load estimated as a wiring load from the circuit cell to the next-stage circuit cell; and
a determining step for comparing the first load related to the load capacitance corresponding to the input load capacitance, and the second load in size, and judging a signal waveform inputted to the next-stage circuit cell to be less than or equal to a predetermined waveform rounding limit value and drivable when the second load is smaller than the first load.
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Accused Products
Abstract
In a method of and an apparatus for designing a semiconductor integrated circuit device, which are capable of causing each waveform rounding to fall within a predetermined limit value without delay calculations at an early stage of the development of the semiconductor integrated circuit device, a wiring path resistance Rpath from an output terminal of a target circuit cell to a next-stage circuit cell and an allowable longest wiring resistance RtL drivable by the target circuit cell are compared. When Rpath is less than or equal to RtL (S4: YES), the sum Rtotal of resistances of wiring loads in a net and RtL are compared. If Rtotal is less than or equal to RtL (S5: YES), then the next-stage circuit cell is judged to be drivable within a predetermined waveform rounding limit value. When Rtotal is greater than RtL (S5: NO), an effective resistance Rw of each wiring load and an allowable longest wiring effective resistance RwL are compared. When Rw is less than or equal to RwL (S6: YES), the waveform rounding at the next-stage circuit cell is judged to fall within a predetermined limit value.
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Citations
13 Claims
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1. A method of designing a semiconductor integrated circuit device, which lays out and wires a circuit cell group according to net information, comprising:
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a longest wiring load calculating step for calculating a wiring load of a drivable allowable longest wiring having taken into consideration a waveform rounding, as a first load for each load capacitance driven by the circuit cell;
a wiring load estimating step for calculating an input load capacitance of a next-stage circuit cell and a second load estimated as a wiring load from the circuit cell to the next-stage circuit cell; and
a determining step for comparing the first load related to the load capacitance corresponding to the input load capacitance, and the second load in size, and judging a signal waveform inputted to the next-stage circuit cell to be less than or equal to a predetermined waveform rounding limit value and drivable when the second load is smaller than the first load. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 13)
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11. An apparatus for designing a semiconductor integrated circuit device, which lays out and wires a circuit cell group according to net information, comprising:
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longest wiring load calculating unit for calculating a wiring load of a drivable allowable longest wiring having taken into consideration a waveform rounding, as a first load for each load capacitance driven by the circuit cell;
wiring load estimating unit for calculating an input load capacitance of a next-stage circuit cell and a second load estimated as a wiring load from the circuit cell to the next-stage circuit cell; and
determining unit for comparing the first load related to the load capacitance corresponding to the input load capacitance, and the second load in size, and judging a signal waveform inputted to the next-stage circuit cell to be less than or equal to a predetermined waveform rounding limit value and drivable when the second load is smaller than the first load. - View Dependent Claims (12)
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Specification