Vlsi Technology, Inc.

Vsli Technology, Inc.

Sunil V Ashtaputre

Moazzem M Hossain

Mark R Hartoog

Siu-Tong Hui

Ying-Meng Li

Jacob Greidinger

Kieu-Huong Do

Bala Thumma

Dale M Wong

Daniel R Brasen

Charles H Ng

Prasad Sakhamuri

Rajiv C Mody

A method for laying out an integrated circuit design based upon a netlist provided by a behavioral synthesis tool includes the steps of: (A) placing cells specified by the netlist in a layout area in a placement step, the cells including pins that are interconnected by nets; (B) verifying timing constraints in a timing verification step of the placed cells in the layout area; and (C) if the timing verification step indicates that timing does not verify in that the timing constraints are not met: (a) modifying the netlist pursuant to an engineering change order (ECO); and (b) making an ECO placement of at least one cell into the layout area by (i) picking an unplaced cell from a set of unplaced cells to be a picked cell; (ii) determining a target window within said layout area for the placement of said picked cell; (iii) mapping said picked cell inside said target window; (iv) removing said picked cell from said set of unplaced cells; (v) optimizing the placement of said picked cell by analyzing said picked cell within said target window with respect to other cells, and modifying said placement of said picked cell if it improves timing; and (vi) repeating steps (i)-(v) until said set of unplaced cells is empty. A layout tool implements the method on a computer system to form a portion of an integrated circuit fabrication system.

Method and apparatus for improving engineering change order placement in

The present invention discloses a method and an apparatus for making digital integrated circuits by considering ramp delay and clock skew as constraints while minimizing the number of inserted buffers and overall wire length connecting components for large clock trees. The invention includes developing a set of circuit specifications including maximum clock skew, minimum driveability, and maximum ramp delay. These specifications are described in a hardware description language on a digital computer system, and a netlist is synthesized from this hardware description. A modified netlist is then formed by analyzing the netlist and inserting buffers into it to satisfy the circuit specifications of skew, driveability, and ramp delay. Thereafter, a digital integrated circuit is produced as specified by the modified netlist.

Method and apparatus for making integrated circuits by inserting buffers

A method for laying out an integrated circuit design based upon a netlist provided by a behavioral synthesis tool includes the steps of: (a) placing cells specified by the netlist in a layout area in a placement step, the cells including pins that are interconnected by nets; (b) verifying timing constraints in a timing verification step of the placed cells in the layout area; and (c) if the timing verification step indicates that timing does not verify in that the timing constraints are not met: (i) modifying the netlist pursuant to an engineering change order (ECO); and (ii) making an ECO placement of at least one cell into the layout area based upon the timing constraints while adjusting any affected nets as specified by the netlist. A layout tool implements the method on a computer system to form a portion of and integrated circuit fabrication system.

Method and apparatus for implementing engineering change orders in

A method of optimizing the placement of components of an integrated circuit to ensure that all circuit paths will meet their timing criteria, as well as to minimize area and total wire length is disclosed. The method employs a non-constant net weighting distribution along critical paths to encourage a mincut algorithm to place components so that path lengths are minimized as well as the entire nets coupled to paths. The magnitude of weights assigned are commensurate with the slack the path has with respect to its maximum delay constraint, as well as the level of method iteration. Any nets not deemed critical are assigned a minimum capacitance constraint to prevent them from becoming critical as a function of actual placement. Weights assigned to capacitively constrained nets are inversely proportional to the difference between the maximum capacitance allowed and the estimated capacitance of the current placement. A novel manner of estimating the propagation delay along the interconnect of the critical path is implemented. A novel weighting of driver/buffer pairs ensure that the most sensitive nets of the pairs are kept short.

Interactive time-driven method of component placement that more directly

The present invention discloses a method and an apparatus for making digital integrated circuits by considering ramp delay and clock skew as constraints while minimizing the number of inserted buffers and overall wire length connecting components for large clock trees. The invention includes developing a set of circuit specifications including maximum clock skew, minimum driveability, and maximum ramp delay. These specifications are described in a hardware description language on a digital computer system, and a netlist is synthesized from this hardware description. A modified netlist is then formed by analyzing the netlist and inserting buffers into it to satisfy the circuit specifications of skew, driveabilility, and ramp delay. Thereafter, a digital integrated circuit is produced as specified by the modified netlist.

A floor-plan of component blocks of logical circuits, including the symbolic routing of major connection networks, is produced as part of the process for laying out an integrated circuit on a chip. The floor-plan is produced before performing optimized placement and routing of logical circuits within component blocks of the VLSI circuit. First, the logical circuits are apportioned into component blocks. Then, an initial lay out of the component blocks of the VLSI circuit is performed. The major connection networks are routed between the component blocks so that the major connection networks are connected to connection areas within the component blocks. The initial lay out of component blocks is adjusted as necessary in order to take into account the addition of the major connection networks. Once any needed adjustments are made, routing guidance information is generated as part of the floor plan. The routing guidance information indicates locations and sizes of the major connection networks.

Symbolic routing guidance for wire networks in VLSI circuits

In a method for providing routing between logic cells, the logic cells are arranged in rows. Intercell connectors within each row of logic cells are aligned, for example in the middle of the rows, to form channel boundaries. The intercell connectors are then channel routed in metal layers above the logic cells. Alternately, intercell connectors are placed within the logic cells, however, these intercell connectors are not necessarily aligned. For each intercell connector which is not on a boundary of a routing channel, a substitute connector is located at the boundary of a routing channel. The substitute connectors and the intercell connectors which are on the boundaries of the routing channels are channel routed. Length of routing segments are then adjusted to substitute connectors to extend to intercell connectors instead of the substitute connectors.

Method of routing three layer metal gate arrays using a channel router

A method sizes routing channels used to route pads to a logic core. Six channels are defined. The six channels include a first special channel, a second special channel, a left channel, a right channel, a bottom channel and a top channel. The first special channel is immediately below the logic core and within a span of the logic core. The second special channel is immediately above the logic core and within a span of the logic core. The left channel is adjacent to a left side of the logic core, the first special channel and the second special channel. The right channel is adjacent to a right side of the logic core, the first special channel and the second special channel. The bottom channel is adjacent to a bottom side of the left channel, the first special channel and the right channel. The top channel is adjacent to a top side of the left channel, the first special channel and the right channel. Pads are positioned at a top side of the top channel, at a bottom side of the bottom channel, at a left side of the left channel and at a right side of the right channel. After performing a global route through the six channels, the six channels are re-sized based on channel density resulting from channel routing each of the six channels. The re-sizing includes repositioning the pads.

Improved pad ring router

A method of routing interconnections of devices in a planar field by the use of a computer. The method effectively shortens the length of all interconnections, including interconnections which connect points on the same device, in accordance with design rules. Also, the layers constituting the planar field can be assigned weights to effectively minimize the appearance of interconnections in the layer having the highest assigned weight.

Wire length minimization in channel compactor

In a method for placement of components for a VLSI circuit, an initial number of current placements are selected. A greedy optimization is partially performed on each of the current placements. Then, a subset of the current placements which have been partially optimized is selected to be the new current placements. This selection is based on a global cost metric for the current placements. The global cost metric is, for example, based on the total length of all connection line networks for the circuit. The partial optimization and selection are repeated until there is only one current placement. Then, an optimization is performed on the remaining placement to obtain an optimized placement. The optimization is, for example, a completion of the partially performed greedy optimization.

Method for optimally placing components of a VLSI circuit

A system and method for routing interconnections through the layout of an integrated circuit is used in conjunction with a sliceable circuit layout specification that specifies the regions of the layout occupied by circuit components, a specification of the locations of terminals in the layout, and a netlist specifying for each terminal the set of other terminals that are to be connected to it. The regions of the circuit layout not occupied by circuit components are called routing regions. The circuit layout is sequentially sliced, defining a series of rectangular channels, each of which divides a region of the circuit layout containing two or more circuit components into two circuit regions each having at least one circuit component. For each channel, if there are one or more neighboring indented routing regions, a special channel is defined for each such indentation. After the entire routing region is divided into channels and special channels, interconnections are routed through those channels and special channels. In particular, before routing interconnections through each channel, interconnections are routed through the corresponding special channels, if any. A data structure is defined for denoting the sequence in which the channels are defined, the region of the layout occupied by each channel, and for each channel, the region of said layout occupied by each corresponding special channel, if any. The order in which channels are routed corresponds to the sequence in which channels were defined, as denoted in the data structure.

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San Jose, CA, United States of America

Sunil V Ashtaputre