JPH08110917A - Lsi wiring method - Google Patents

Abstract

PURPOSE: To properly select a network in trunk line division for reducing the number of wiring tracks by selecting trunk lines in the network corresponding to a node having ancestor-descendant relation on the route of a master-slave restricting graph as trunk lines to be divided. CONSTITUTION: A master-slave restricting graph and a zone expression diagram are prepared based upon a line connection request and a two-part graph is prepared based upon the zone expression diagram. The matching degree of maximum matching in the two-part graph is calculated. When a prescribed number of nodes is different from the matching degree of maximum matching in the two-part graph, trunk line division is executed. In a two-part graph consisting of zones Z1, Z2, a node having ancestor-descendant relation on route of the master-slave restricting graph between a network 4 corresponding to a node 4 belonging to the zone 2 and a network 1 corresponding to a node 1 belonging to the zone 1 is a node 2. Thereby, trunk lines in the network 2 corresponding to the node 2 are selected as trunk lines to be divided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit design method for an LSI circuit using a standard cell method, and more particularly to an LSI channel wiring method which has a great influence on an increase or decrease in the area of an LSI chip.

[0002]

2. Description of the Related Art As a method for designing a large-scale LSI, a method called a standard cell method is often used. The standard cell method is an LSI design method in which some small-function circuits called cells are prepared, and these are combined to form an LSI circuit. The prepared cell group is called a cell library. The cell library is prepared so that it can be used in common when designing other LSIs.

The above-mentioned cells are standardized in height, position of power supply pins, and terminal direction. Such cells are arranged in rows, and an area between the cell rows is utilized to make a vertical (LSI plan view). The channel wiring method is a method of connecting the terminals of the cells arranged side by side in the plan view (in the case of drawing). The area between the cell rows is called a channel area, and in the channel wiring method, a net (wiring) is usually a trunk line (horizontal line segment) arranged parallel to the terminal row and a net perpendicular to the terminal row. The branch line (vertical line segment) arranged is used. When the trunk line and the branch line are wired in different layers, the trunk line and the branch line are connected by a through hole.

In the channel region, a grid on which the trunk lines and branch lines can be arranged is predetermined. This grid is called a wiring grid, and the grid in the main line direction is called a track. The first track T1, the second track T2, the third track T3, ... Channel wiring is an operation that determines which trunk line is assigned to which track.

By the way, in order to reduce the LSI chip area, the number of tracks used for wiring must be reduced.

In this channel wiring, in order to prevent different nets (wirings) from being electrically short-circuited,
It is necessary to prohibit overlapping of trunk lines and branch lines of different nets, and in this case, the upper and lower constraint graphs are used to prevent overlapping of branch lines. The vertical constraint graph is a graph that defines the vertical positional relationship of the nets (the vertical positional relationship in the plan view of the LSI when the LSI is drawn in the plan view) in order to prevent overlapping of branch lines.

FIG. 13 is a flow chart showing how to create the upper and lower constraint graphs.

First, the number of the net searched for as a net to be assigned (routed) to a track is set to A (S101), and there is a terminal not searched for in the net A (S102). Net A terminal and X
If there is another net that has terminals with the same coordinates (S
103), the number of the net is set to B (S104), and if the Y coordinate of the net A is larger than the Y coordinate of the net B (S105), a directed branch is made from the node A indicating the net A to the node B indicating the net B. Is described (S106). That is, the fact that the Y coordinate of the net A is larger than the Y coordinate of the net B means that the terminal to which the net A is connected exists in the cell row between the cell rows and the terminal to which the net B is connected is
It means that it exists in the cell row below between the cell rows, and in this case, the directional branch is described from the node A indicating the net A to the node B indicating the net B.

On the contrary, if the Y coordinate of the net A is smaller than the Y coordinate of the net B (S105), that is, the terminal to which the net A is connected exists in the cell row below and the terminal to which the net B is connected. Is present in the upper cell column, the directional branch is described from the node B to the node A (S107).

Next, the same operation as described above is repeated for the other terminals of the net A (S102 to S107), and when there are no unsearched terminals of the net A (S102), the same operation as described above is performed for the other unsearched nets. Is repeated (S100
~ S107).

FIG. 14 is a diagram for explaining a conventional example. FIG. 14 (1) shows an example of connection request in the channel wiring, and FIG. 14 (2) shows the connection request based on the connection request. An example of the created vertical constraint graph is shown.

Nodes and directed edges are used in the upper and lower constraint graphs. The "node" is a net number (a number to the right of "N" in the code of the net) enclosed by a circle (other symbols such as a rectangle may be used) (for example, "1" for the net N1). Is surrounded by a circle,
That is,) which net corresponds to. The “directed branch” is an arrow indicating a vertical positional relationship between two nets. For example, if net N1 should be assigned to a track on net N5, node 1 () through node 5
Enter the directional branch toward ().

Next, how to create the upper and lower constraint graphs will be concretely described.

First, in the connection request shown in FIG. 14A, the terminal 1 located at the leftmost of the terminals in the upper cell row.
Node 1 (that is) corresponding to the net N1 to which is connected, and the terminal arranged at the same position on the X axis as the terminal of the net N1 corresponding to this node 1 is the terminal 2, and the terminal 2 is Since node 1 exists in the upper cell column and terminal 1 exists in the lower cell column, node 2 (that is,) of net N2 connected to terminal 2 is written above node 1 and node 2
From FIG. 1 to the node 1, the directional branch is described.

Of the nodes not yet described in the upper and lower constraint graph shown in FIG. 14 (2), the terminals of the node 2 (that is, the node 2) indicating the net N2 are arranged at the same position on the X axis in the same figure. Since the terminal that is connected is the terminal 3, the terminal 3 exists in the upper cell row, and the terminal 2 exists in the lower cell row, the node 3 (that is,) of the net N3 connected to the terminal 3 becomes a node. 2 is described above, and the directional branch is described from the node 3 to the node 2. Here, since there is no other terminal arranged at the same position on the X axis as the terminal of the net N3 corresponding to the node 3, the directional branch toward the node 3 is not described.

Hereinafter, similarly, the node 5 (that is) is described above the node 4, the directional branch is described from the node 5 to the node 4, and the node 6 (that is) is described above the node 5. Then, the directional branch is described from the node 6 to the node 5, and since all the nets to be described in the upper and lower constraint graphs are described in the upper and lower constraint graphs, the upper and lower constraint graphs are completed.

In the drawings, for example, the node 1 is described, but hereinafter, in the specification,
Is shown, only the characters of "node" and its number such as "node 1" are described.

By the way, the upper and lower constraint graph is a graph showing constraints on the arrangement of the nets in the vertical direction of the nets. It is known that the "section graph shown". Here, the "zone representation diagram" is a diagram showing a relationship in which the trunks of different nets overlap each other, and the "section graph showing the horizontal constraint" indicates that the trunks overlap each other in the horizontal direction. ) Is a graph showing the constraint in the horizontal direction of the net.

Next, a method of creating a zone representation diagram will be described.

FIG. 15A is a diagram showing a section graph representing a horizontal constraint created based on the connection request shown in FIG.

In FIG. 15A, a node indicates a trunk line,
An undirected branch indicates that the trunk lines overlap in the horizontal direction.
For example, since the trunk line 2 and the trunk line 3 overlap each other in the horizontal direction, an undirected branch exists between the node indicating the trunk line 2 and the node indicating the trunk line 3 (the inclination of the undirected branch itself has no meaning. ). However, since the trunk line 1 and the trunk line 4 do not overlap in the horizontal direction, there is no undirected branch between the node indicating the trunk line 1 and the node indicating the trunk line 4. Therefore, the section graph for the connection request shown in FIG. 14 is as shown in FIG. 15 (1).

Here, the set of maximum cliques in FIG. 15A forms a zone. The "maximum clique" is a graph having the maximum number of nodes in a simple graph in which a branch exists between any two nodes.

In FIG. 15A, the maximum cliques are {1, 2, 3}, {2, 3, 4}, {4, 5}, {5,
6} and there are four zones. Therefore, FIG.
The zone representation diagram corresponding to the connection request shown in FIG.
It becomes as shown in (2). In the zone representation diagram, trunks sharing the same zone cannot be wired to the same track, but trunks not sharing the zone can be wired to the track at the same position.

On the other hand, one of the channel wiring algorithm
The left edge method is known as one (Hashimoto,
A., Stevens, J., "Wire Routing by Optemizing Chann
el Assignment within Large Apertures ", Proc. 8th D
esign Automation Workshop, 1971, 155-169).

In the "left edge method", a directional branch indicating a vertical positional relationship between the nets is described between a plurality of nodes respectively indicating a plurality of nets connecting cell columns in the LSI. Using the vertical constraint graph
Of the orphan nodes (the nodes in which the directional branch toward the given node is not described in the upper and lower constraint graphs), the net corresponding to the orphan node located on the leftmost is assigned to the end of the track, Determine whether another net can be assigned to the assigned track, and when another net cannot be assigned to that track, the node corresponding to the already assigned net and its directional branch Is deleted from the upper and lower constraint graphs, and the same operation as described above is repeated, thereby allocating the remaining nets one track at a time to the tracks next to the track after the allocation is completed.

That is, in the left edge method, when tracks are allocated with upper and lower constraints, only the parentless node existing at the top in the upper and lower constraint graph is the target of track allocation, and the net allocation is one track. Every time the process is finished, the node corresponding to the net and the directed branch emerging from this node are deleted from the upper and lower constraint graphs. Further, the nets may be sequentially allocated from the upper track to the lower track, or the nets may be sequentially allocated from the lower track to the upper track. In other words, it is a wiring method in which nets are sequentially allocated while shifting one track from the endmost track.

FIG. 16 is a diagram showing a wiring result when the left edge method is applied based on the connection request shown in FIG.

[0028]

By the way, in the channel wiring, the trunk line division is an important method. This "main line division" is a method of dividing one main line into two or more lines, and is used when the number of tracks required for wiring (the number of wiring tracks) is reduced and the channel width is reduced.

FIG. 17 is a diagram showing a connection request used when showing that the channel width becomes smaller when the trunk line is divided, and a vertical constraint graph based on the connection request.

If the connection request shown in FIG. 17 is wired without dividing the trunk line, three tracks are required as shown in FIG. However, as shown in FIG. 19, if the net 2 is divided into main lines at the position a, the wiring for the connection request shown in FIG. 17 can be realized with only two tracks. By this division of the main lines, as compared with the case shown in FIG. The area required for the channel wiring for one track can be reduced.

However, as shown in FIG. 20, when the net 2 is divided into main lines at the position b, the number of tracks required for wiring is 3, and even if the main lines are divided, the number of necessary tracks does not decrease. Further, as shown in FIG. 21, when the net 3 is divided into main lines, the number of tracks required for wiring is 3,
Also in this case, the number of tracks required does not decrease even if the trunk line is divided.

As described above, the number of wiring tracks can be reduced by executing the trunk line division, but it is important to select the net for the trunk line division and to determine the position of the trunk line division. Since there is no objective method for selecting a net for main line division and selecting a position for main line division, there is a problem that the number of wiring tracks cannot be efficiently reduced.

According to the present invention, a vertical constraint in which a directional branch indicating a vertical positional relationship between the nets is described between a plurality of nodes respectively indicating a plurality of nets connecting cell columns in an LSI. In an LSI wiring method for wiring an LSI based on a graph, it is possible to appropriately select a net in a trunk line division for reducing the number of wiring tracks, and a trunk line in a trunk line division for reducing the number of wiring tracks. An object of the present invention is to provide an LSI wiring method capable of appropriately selecting a division position and further reliably performing automatic trunk line division.

[0034]

According to a first aspect of the present invention, when a predetermined number of nodes and a matching degree of maximum matching of a bipartite graph are different from each other, a trunk line is divided and one of two zones is divided. Then, the nets corresponding to the nodes belonging to the first zone and the nets corresponding to the nodes belonging to the second zone are the trunk lines of the nets corresponding to the nodes having the ancestor-descendant relation on the path of the upper and lower constraint graphs. , Is selected as a target of the trunk line division.

According to the second aspect of the present invention, among the terminals of the trunk line to be divided, one of the two trunk lines having the ancestor-descendant relationship which is closest to one trunk line and the above-mentioned two terminals having the ancestor-descendant relationship. The position between the main line and the terminal closest to the other main line is selected as the position to be divided into main lines.

According to the invention described in claim 3, two nodes corresponding to two trunk lines after one trunk line is divided are described in a section graph showing a horizontal constraint, and a section graph showing the horizontal constraint is shown. , An undirected branch is placed between the two nodes.

[0037]

According to the invention described in claim 1, the predetermined number of nodes and 2
When the matching degree of the maximum matching of the partial graph is different, the trunk line is divided, and the net corresponding to the node belonging to the first zone of the two zones and the node belonging to the second zone. Since the trunk of the net corresponding to the node having an ancestor-descendant relation on the route of the upper and lower constraint graph with the net corresponding to is selected as the target of the trunk line division, in the LSI wiring method of wiring the LSI based on the upper and lower constraint graph. Therefore, it is possible to appropriately select the target trunk line for the trunk line division to reduce the number of wiring tracks.

According to the second aspect of the present invention, among the terminals of the trunk line to be divided, the terminal closest to one of the two trunk lines having the ancestor-descendant relationship and the two terminals having the ancestor-descendant relationship. Since the position between the terminal closest to the other main line of the main lines is selected as the position to be divided into main lines, the position of the main line division in the target main line to reduce the number of wiring tracks is appropriately selected. You can choose.

In the invention according to claim 3, two nodes corresponding to two trunk lines after one trunk line is divided are described in a section graph showing a horizontal constraint, and a section graph showing the horizontal constraint is shown. In the above, since the undirected branch is provided between the two nodes, it is possible to prevent the divided two main lines from being routed to the same track, so that the automatic main line division can be surely executed.

[0040]

1 is a flow chart showing an embodiment of the present invention.

FIG. 2 (1) is a diagram showing a connection request in the above embodiment, and FIG. 2 (2) is a diagram showing a vertical constraint graph created based on the connection request shown in FIG. 2 (1). 2 (3) is a zone representation diagram created based on the connection request shown in FIG. 2 (1). 2 (1),
FIG. 2 (2) is the same diagram as the conventional example shown in FIGS. 14 (1) and 14 (2), and FIG. 2 (3) is the same as the zone representation diagram in the conventional example shown in FIG. 15 (2). It is a thing.

First, the upper and lower constraint graphs shown in FIG.
A zone representation diagram (zone representation) shown in FIG. 2C is created (S1). Then, the number n of zones is set to "1" (S2) and a bipartite graph is created (S2).
3, S4).

FIG. 3 is a diagram showing a bipartite graph of zones Z1 and Z2 created based on the zone representation diagram shown in FIG. 2 (3).

That is, when the zone Z1 and the zone Z2 in the zone representation diagram showing the relationship in which the trunks of different nets overlap each other are adjacent to each other, a set of nodes indicating trunks belonging to the zone Z1 and not belonging to the zone Z2 is L ( Figure 3
, A set of nodes indicating a trunk line that belongs to the zone Z2 and does not belong to the zone Z1 is set to R (node 4 in FIG. 3), and a node that belongs to the set L of nodes and a set of nodes R Let E (none in FIG. 3) be a set of undirected branches described between the nodes to which the nodes belong and that represent each of the plurality of trunk lines that can be wired on the same track, and are set as E (none). By 2
A division graph is created.

Note that the bipartite graph is a concept in graph theory, and when vertices (nodes) are divided into two groups due to differences in properties, there is a branch only between one group and the other group. The graph is called a bipartite graph. In the above embodiment, in the zone representation shown in FIG. 2C, a set L of nodes belonging to the left zone (for example, Z1) of two adjacent zones and a right zone (for example, Z2) are included. Considering the set R of nodes to which it belongs, the element l of the set L of nodes and the element r of the set R of nodes
Since the branch (undirected branch) is set only when and can be wired to the same track, the branch (undirected branch) exists only between the node set L and the node set R. Therefore, the graph constructed in the above embodiment is one mode of the bipartite graph.

In the upper and lower constraint graph, a directional branch of 4 → 2 → 1 is set up between node 1 and node 4, and node 1
Since the node 4 and the node 4 are restricted in the vertical direction, they cannot be wired in the same track. Therefore, a branch cannot be set up between the node 1 and the node 4 in the bipartite graph, that is, there is no direction between the node 1 which is the set L of nodes and the node 4 which is the set R of nodes. Branch E cannot be listed.

Nodes 2 and 3 are zone Z
Since both 1 and Z2 exist, they are indicated by broken lines in FIG. 3 for reference, but since both zones Z1 and Z2 exist, 2
It is not finally described in the subgraph.

Next, the matching order of the maximum matching of the bipartite graph is calculated (S5). Here, the matching order of the maximum matching in the bipartite graph is the number of undirected branches described between the nodes belonging to the zone Z1 and the nodes belonging to the zone Z2 in the bipartite graph (the number of pairs of nodes). ), And in the bipartite graph shown in FIG. 3, the number of branches (the number of pairs) between the node 1 and the node 4 is “0”, so the matching order of the maximum matching is “0”.

That is, generally, matching in a bipartite graph is to select a set of nodes such that two branches belonging to a subset of branches of the graph do not enter the same node. In other words, a pair of nodes in which two nodes are connected by a branch in a one-to-one relationship is said to be matched in a bipartite graph. Then, the maximum matching is a matching in which the number of the above-mentioned one-to-one node pairs is the largest.

Matching in the above embodiment is as shown in FIG.
In step S5 shown in FIG.
It is to create a _k and the node node of the pair by the elements r _k of the set R of. The maximum matching in the above embodiment is to select a pair of trunk nodes so that the number of trunk pairs is the largest in the bipartite graph constructed in step S4 shown in FIG. Further, the matching order of the maximum matching is the number of pairs of the above-mentioned 1: 1 node.

Next, when the smaller number of the number of nodes belonging to the zone Z1 and the number of nodes belonging to the zone Z2 is set as the "predetermined number of nodes", the predetermined number of nodes is "1", The predetermined number of nodes "1" is compared with the matching degree "0" of the maximum matching of the bipartite graph (S6). On the other hand, when the predetermined number of nodes is different from the matching order of the maximum matching, the trunk line division is performed. Therefore, in the above case, the trunk line division is performed.

Next, the procedure for selecting a net to be the subject of trunk line division will be described.

In the bipartite graph of the zones Z1 and Z2 shown in FIG. 3, the net 4 corresponding to the node 4 belonging to the zone Z2 and the net 1 corresponding to the node 1 belonging to the zone Z1 are on the path of the upper and lower constraint graphs. Then, the node having the ancestor-descendant relation is the node 2, and the trunk line of the net 2 corresponding to this node 2 is selected as the target of the trunk line division (S11 to S15).

In the upper and lower constraint graphs, if the starting node is u and the ending node is v,
It is said that the node v can be reached from the node u, the node u is in an ancestor relation of the node v, and the node v is the node u.
Therefore, the above "in ancestor-descendant relationship" means the above-mentioned ancestor relationship or the above-mentioned descendant relationship.

That is, in the above embodiment, the set L of nodes is set.
If the matching order of the maximum matching of the bipartite graph is smaller than the smaller number of the number of nodes belonging to R and the number of nodes belonging to the set R of nodes, then any arbitrary R belonging to the set R of nodes in the upper and lower constraint graphs Trunk line r
And a trunk line d of the trunk lines belonging to the set L of nodes between the trunk line r and the trunk line 1 having an ancestor-descendant relationship.
Is selected as the target of the trunk line division.

In the above embodiment, when the predetermined number of nodes in the two zones and the matching degree of the maximum matching of the bipartite graph are different, the trunk line is divided.
Of the two zones, the net corresponding to the node belonging to the first zone and the net corresponding to the node belonging to the second zone are nodes that are in ancestor-descendant relation on the path of the upper and lower constraint graphs. Since the trunk line of the corresponding net is selected as the target of the trunk line division, in the LSI wiring method for wiring the LSI based on the upper and lower constraint graph, it is necessary to properly select the net in the trunk line division for reducing the number of wiring tracks. You can

Next, a method of deciding a main line division position for deciding which of the main lines selected as the main line division targets to be divided will be described.

In the above case, the main line 2 is selected as the target of the main line division, and the main line 2 can be physically divided into the main lines. This condition is the X coordinate of the leftmost pin of the net 4. , There is a space (lattice in which branch lines can be arranged in the channel region) to be divided into main lines between the right end pin of the net 1 and the X coordinate, and in this sense, the main line 2 is physically Since the trunk line can be divided (S2
1), the division position d2 of the trunk line 2 is determined as follows.

That is, the X coordinate of the terminal of the trunk line 4 closest to the trunk line 1 is P _4L , the X coordinate of the terminal of the trunk line 1 closest to the trunk line 4 is P _1R , and P _1R <d2 <P _4L is satisfied. The main line is divided at the X coordinate d2 (S22, S23). d
The position 2 is shown in FIG. The nets obtained by dividing the net 2 into two trunk lines will be referred to as nets 2 ₁ and 2 ₂ .

That is, in the above embodiment, between the position X _{rL of the} terminal closest to the trunk line l among the terminals of the trunk line r and the position X _{lR of the} terminal closest to the trunk line r of the terminals of the trunk line l. The position X _d is selected as a division position where the trunk line d should be divided.

In the above embodiment, among the terminals of the trunk line to be divided, the terminal closest to one of the two trunk lines in the ancestor-descendant relation and the one of the two trunk lines in the ancestor-descendant relation. The position between the terminal closest to the other trunk line,
Since the position is selected as the position for main line division, the position of main line division in the main line division performed to reduce the number of wiring tracks can be appropriately selected.

Then, the net r is removed from the set R of nodes and the net l is removed from the set L of nodes 1 (S32).

Next, the horizontal constraint setting will be described.

FIG. 4 is a diagram showing a vertical constraint graph after the trunk line 2 is divided into the trunk line 2 ₁ and the trunk line 2 ₂ .

This horizontal constraint setting is to constrain the trunk line 2 ₁ and the trunk line 2 ₂ into which the trunk line 2 is divided from being wired in the same track. That is, an undirected branch is described between the nodes 2 ₁ and 2 ₂ in the section graph showing the horizontal constraint (S31). This prevents the trunk lines 2 ₁ and 2 _{2 from} being laid on the same track thereafter.

In the above embodiment, the two main lines obtained by dividing the main line d at the position X _d are restricted so as to prevent the two main lines from being wired in the same track.

FIG. 5 shows the net 2 in the horizontal constraint graph.
It is a figure which shows the state in which the undirected branch is stretched between ₁ and 2 ₂ .

In the above embodiment, two nodes corresponding to two trunk lines after one trunk line is divided are described in a section graph showing a horizontal constraint, and in the section graph showing the horizontal constraint, two nodes are described. Since the undirected branch is provided between the two nodes, it is possible to prevent the divided two main lines from being routed to the same track, so that the automatic main line division can be surely executed.

FIG. 6 is a diagram showing a zone representation after the trunk line 2 is divided. After dividing the main line, the zone Z2 will be referred to as _two zones Z2 ₁ and Z2 ₂ .

Then, the upper and lower constraint graphs and the zone representation diagram are updated (S41), and the bipartite graph is updated (S42).

In this way, the smaller number of the number of nodes belonging to the zone Z1 and the number of nodes belonging to the zone Z2 and the matching order of the maximum matching of the bipartite graph become the same (S6), and the trunk line Since it is not necessary to perform division, n indicating the number of zones is incremented by 1 (S7), and a bipartite graph for the next zone and the next zone is created (S4), that is, zones Z2 and Z.
Whether or not it is necessary to perform trunk line division by creating a bipartite graph for 3 and 3, calculating the matching order of the maximum matching of the bipartite graph (S5), and comparing the matching order with a predetermined number of nodes. (S
6).

When it is determined in step S6 that the matching order and the predetermined number of nodes are different from each other a predetermined number of times (for example, 10 times), the step S6 is actually executed.
The process proceeds to step 7 and the process is performed for the next zone. When the result that the matching order and the predetermined number of nodes are different is given a predetermined number of times (for example, 10 times),
There may be a case where the trunk line cannot be physically divided, for example, the length of the trunk line is only one terminal.

As a result of the trunk line division as described above, zone Z
Since 2 is divided into zones Z2 ₁ and Z2 ₂ , the above processing is applied to zones Z2 ₂ and Z ₃ in the updated zone representation diagram.

That is, first, a bipartite graph is created (S
4) At this time, the set L of nodes indicating the trunk lines that belong to the zone Z2 ₂ but not to the zone Z ₃ is the node 2 ₂ and the node 3
And a set R of nodes indicating a trunk line that belongs to the zone Z ₃ but does not belong to the zone Z _{2 2} is the node 5.

In the vertical constraint graph shown in FIG. 5, since the node 2 ₂ and the node 5 are vertically constrained, they cannot be wired on the same track, and the node 3 and the node 5 are vertically constrained. Since it is not applied, wiring can be made on the same track, and therefore, an undirected branch can be provided between the node 3 and the node 5 in the bipartite graph.

FIG. 7 is a diagram showing a bipartite graph created as described above for the zone Z2 ₂ and the zone Z3.

Since the number of undirected branches stretched between the node 3 and the node 5 shown in FIG. 7 is "1", the maximum matching order is "1", and the predetermined node The number is “1”, which is the smaller number of the number of nodes belonging to the zone Z2 ₁ and the number of nodes belonging to the zone Z3 (S5). Then, the order of maximum matching is "1".
And the predetermined number "1" are equal (S6), the trunk line division is not performed.

Next, the above processing is applied to the zones Z3 and Z4.

First, a bipartite graph is created for zone Z3 and zone Z4. That is, it belongs to zone Z3 and Z4
A set L of nodes indicating a trunk line that does not belong to Z is net 4, and a set R of nodes indicating a trunk line that belongs to zone Z4 but does not belong to Z3 is net 6. In the top-bottom constraint graph shown in FIG. 5, since the top-bottom constraint is imposed on node 4 and node 6, it is not possible to wire on the same track, and therefore there is no space between node 4 and node 6 in the bipartite graph. I can't put up a branch.

FIG. 8 is a diagram showing a bipartite graph created as described above for zone Z3 and zone Z4.

In FIG. 8, since the number of undirected branches between the nodes 4 and 6 is "0", the maximum matching order is "0" and the predetermined number of nodes is "1". , The maximum matching order is different from the predetermined number of nodes, so trunk line division is performed.

In this case, in the upper and lower constraint graph shown in FIG. 5, since the net 5 exists on the route between the node 4 and the node 6, the trunk line 5 corresponding to the net 5 is the target of trunk line splitting. .

The division position d5 of the trunk line 5 is
Let P _{4R be} the X coordinate of the terminal closest to the main line 6 and P _{6L be} the X coordinate of the terminal closest to the main line 4 of the main line 6, P _4R <
d5 <Z coordinate d5 which satisfies P _6L is a position for performing main line division. The position of d5 is shown in FIG. The nets obtained by dividing the net 5 into trunk lines are called nets 5 ₁ and 5 ₂ .

Next, in order to prevent the trunk line 5 ₁ and the trunk line 5 ₂ from being divided into the trunk lines by being wired in the same track, a horizontal constraint is set between the nets 5 ₁ and 5 ₂ . To provide this horizontal constraint, an undirected branch is set between the net 5 ₁ and the net 5 ₂ in the horizontal constraint graph.

FIG. 9 shows the net 5 in the horizontal constraint graph.
_1, 5 undirected between ₂ is a diagram showing a state of being stretched.

In FIG. 10, the trunk line 5 is divided into trunk line 5 ₁ and trunk line 5 _2.
It is a figure which shows the up-and-down constraint graph after dividing into and.

FIG. 11 is a diagram showing a zone representation after the trunk line 5 is divided. After the trunk line 5 is divided, the zone Z4 is divided into the zone Z4 ₁ and the zone Z4 ₂ .

As described above, since the number of zones n reaches its maximum value n _max (4) (S3), the trunk line dividing process is terminated.

FIG. 12 is a diagram showing a result of performing trunk line division in the above-described embodiment and then performing wiring by the left edge method.

As shown in FIG. 12, in the above-mentioned embodiment, the number of wiring tracks is sufficient to be three tracks. On the other hand, when wiring is performed without dividing the trunk line, five tracks are required as shown in FIG. Therefore, in the above embodiment, the number of wiring tracks is reduced by 2 tracks.

[0091]

According to the invention described in claim 1, the LSI
In the above, the LSI is wired based on the vertical constraint graph in which the directional branch indicating the vertical positional relationship between the nets is described between the plurality of nodes respectively indicating the plurality of nets connecting the cell columns. In the LSI wiring method, it is possible to appropriately select a net in the trunk line division for reducing the number of wiring tracks.

According to the second aspect of the present invention, it is possible to properly select the net in the trunk line division for reducing the number of wiring tracks, and at the same time, the trunk line in the trunk line division for reducing the number of wiring tracks. This has the effect of being able to appropriately select the position of division.

According to the third aspect of the present invention, it is possible to properly select the net in the trunk line division for reducing the number of wiring tracks, and at the same time, the trunk line in the trunk line division for reducing the number of wiring tracks. There is an effect that the position of division can be appropriately selected, and further, the automatic trunk line division can be surely executed.

[Brief description of drawings]

FIG. 1 is a flowchart showing an embodiment of the present invention.

FIG. 2 is a diagram showing a connection request, a vertical constraint graph, and a zone representation diagram in the above embodiment.

FIG. 3 is a diagram showing a bipartite graph of zones Z1 and Z2 created based on the zone representation diagram shown in FIG. 2 (3).

FIG. 4 is a diagram showing a vertical constraint graph after the trunk line 2 is divided into a trunk line 2 ₁ and a trunk line 2 ₂ .

FIG. 5 is a diagram showing a state in which an undirected branch is stretched between the nets 2 ₁ and 2 _{2 in} the horizontal constraint graph.

FIG. 6 is a diagram showing a zone representation after the trunk line 2 is divided.

FIG. 7 is a diagram showing a bipartite graph created for zone Z2 ₂ and zone Z3.

FIG. 8 is a diagram showing a bipartite graph created for zone Z3 and zone Z4.

FIG. 9 is a diagram showing a state in which an undirected branch is stretched between the nets 5 ₁ and 5 _{2 in} the horizontal constraint graph.

FIG. 10 is a diagram showing a vertical constraint graph after the trunk line 5 is divided into a trunk line 5 ₁ and a trunk line 5 ₂ .

FIG. 11 is a diagram showing a zone representation after the trunk line 5 is divided.

FIG. 12 is a diagram showing a result of performing trunk line division and wiring by the left edge method in the above-described embodiment.

FIG. 13 is a flowchart showing how to create an upper and lower constraint graph.

FIG. 14 is a diagram illustrating an example of a wire connection request for explaining a conventional example and a vertical constraint graph created based on the wire connection request.

15 is a diagram showing a section graph and a zone representation diagram showing horizontal constraints created based on the connection request shown in FIG.

16 is a diagram showing a wiring result when the left edge method is applied based on the connection request shown in FIG.

FIG. 17 is a diagram showing a connection request used when it is shown that the channel width becomes smaller when the trunk line is divided, and a vertical constraint graph based on the connection request.

FIG. 18 is a diagram showing an example of wiring for the connection request shown in FIG. 17 without performing trunk line division.

FIG. 19 is a diagram showing an example in which the net 2 is divided into main lines at a position a.

FIG. 20 is a diagram showing an example in which the net 2 is divided into main lines at a position b.

FIG. 21 is a diagram showing an example in which the net 3 is divided into main lines.

[Explanation of symbols]

Z1, Z2, Z2 ₁ , Z2 ₂ , Z3, Z4, Z4 ₁ , Z
4 ₂ ... Zones, n ... Number of zones, R ... Set of unmatched nodes in right zone of bipartite graph, L ... Set of unmatched nodes in left zone of bipartite graph, r ... Node Nodes belonging to the set R, l ... Nodes belonging to the set L of nodes, d ... Nodes to be divided, Xd ... Division positions of trunk lines to be divided.

Claims (4)

[Claims] 1. A vertical constraint graph in which a directional branch indicating a vertical positional relationship between the nets is described between a plurality of nodes respectively indicating a plurality of nets connecting cell columns in an LSI. L to wire LSI based on
In the SI wiring method, when the first zone and the second zone in the zone representation diagram showing the relationship in which the trunks of different nets overlap each other are adjacent to each other, they belong to the first zone and belong to the second zone. A set L of nodes indicating an unmaintained trunk line and the second
, A set of nodes indicating a trunk line that belongs to the zone 1 and a group that does not belong to the first zone, and a node belonging to the set L of the nodes and a node belonging to the set R of the nodes. A set E of undirected branches described between a plurality of nodes indicating each of a plurality of possible trunk lines
A bipartite graph creating step of creating a bipartite graph composed of; and the number of nodes belonging to the set L of nodes and the number of nodes belonging to the set R of nodes being smaller than When the matching order of the maximum matching of the subgraph is small, among the arbitrary trunk line r belonging to the set R of the nodes and the trunk line belonging to the set L of the node in the upper and lower constraint graph, the trunk line r and the ancestor descendant relation And a trunk line d located on the path between the trunk line l and the trunk line l. 2. An up-and-down constraint graph in which a directional branch indicating a vertical positional relationship between the nets is described between a plurality of nodes respectively indicating a plurality of nets connecting cell columns in an LSI. L to wire LSI based on
In the SI wiring method, when the first zone and the second zone in the zone representation diagram showing the relationship in which the trunks of different nets overlap each other are adjacent to each other, they belong to the first zone and belong to the second zone. A set L of nodes indicating an unmaintained trunk line and the second
, A set of nodes indicating a trunk line that belongs to the zone 1 and a group that does not belong to the first zone, and a node belonging to the set L of the nodes and a node belonging to the set R of the nodes. A set E of undirected branches described between a plurality of nodes indicating each of a plurality of possible trunk lines
A bipartite graph creating step of creating a bipartite graph composed of; and the number of nodes belonging to the set L of nodes and the number of nodes belonging to the set R of nodes being smaller than When the matching order of the maximum matching of the subgraph is small, among the arbitrary trunk line r belonging to the set R of the nodes and the trunk line belonging to the set L of the node in the upper and lower constraint graph, the trunk line r and the ancestor descendant relation A trunk line selection step of selecting a trunk line d located on the path between the trunk line l and the trunk line l, which is the target of the trunk line split; a position X _{rL of} a terminal closest to the trunk line l among the terminals of the trunk line r, Of the terminals of the trunk line l, the trunk line r
And a position X _d between the position X _{lR of the} terminal closest to the position x and a position X _d for selecting the dividing position to divide the trunk line d. 3. A vertical constraint graph in which a directional branch indicating a vertical positional relationship between the nets is described between a plurality of nodes respectively indicating a plurality of nets connecting cell columns in an LSI. L to wire LSI based on
In the SI wiring method, when the first zone and the second zone in the zone representation diagram showing the relationship in which the trunks of different nets overlap each other are adjacent to each other, they belong to the first zone and belong to the second zone. A set L of nodes indicating an unmaintained trunk line and the second
, A set of nodes indicating a trunk line that belongs to the zone 1 and a group that does not belong to the first zone, and a node belonging to the set L of the nodes and a node belonging to the set R of the nodes. A set E of undirected branches described between a plurality of nodes indicating each of a plurality of possible trunk lines
A bipartite graph creating step of creating a bipartite graph composed of; and the number of nodes belonging to the set L of nodes and the number of nodes belonging to the set R of nodes being smaller than When the matching order of the maximum matching of the subgraph is small, among the arbitrary trunk line r belonging to the set R of the nodes and the trunk line belonging to the set L of the node in the upper and lower constraint graph, the trunk line r and the ancestor descendant relation A trunk line selection step of selecting a trunk line d located on the path between the trunk line l and the trunk line l, which is the target of the trunk line split; a position X _{rL of} a terminal closest to the trunk line l among the terminals of the trunk line r, Of the terminals of the trunk line l, the trunk line r
A position X _d between the position X _{lR of the} terminal closest to the position X _d and a position for selecting the main line d as a division position to be divided; and a position obtained by dividing the main line d at the position X _d. And a horizontal constraint setting step of constraining that two trunk lines are prevented from being routed to the same track. 4. The trunk line division according to claim 1, wherein all the zones in the zone representation diagram are divided into tracks, and tracks are assigned to the divided trunk lines. LSI wiring method.