Net

A net may either be a connection of at least two gates or a global input or output to the entire netlist. A net connects to a gate via the pins provided by the gate. The association of a net to a pin and its gate is stored within a so called endpoint.

Net Information and Management

A new net can be created using the create_net function on the netlist. Each net has a unique ID and a name and may be part of a grouping. All these information are accessible using the get_id, set_name, get_name, and get_grouping functions.

net = netlist.create_net("example_net")   # create a net with name "example_net"
net.get_id()                              # get the ID of the net
net.get_name()                            # get the name of the net
net.get_grouping()                        # get the grouping of the net

A net can be accessed by ID using the get_net_by_id function and may be deleted from the netlist using delete_net:

net = netlist.get_net_by_id(3)
netlist.delete_net(net)

Net Sources and Destinations

Each net keeps track of its source (gate output) and destination (gate input) endpoints. Such endpoints may be added using add_source and add_destination. A list of source and destination endpoints can be retrieved using get_sources and get_destinations. Endpoints may also be removes from a net using remove_source and remove_destination.

net = netlist.create_net("example_net")   # create a new net
gate = netlist.get_gate_by_id(3)          # get gate with ID 3 (assumed to have a pin called "A")
net.add_destination(gate, "A")            # add pin "A" of gate with ID 3 as destination of net
dest = net.get_destinations()[0]          # get first (and in this case only) destination
net.remove_destination(dest)              # remove the destination again

Additional commands allow to determine whether an endpoint is a source or a destination of a net and to get the total number of sources and destinations. These are given by is_a_source, is_a_destination, get_num_of_sources, and get_num_of_destinations.

Special Nets

All nets that have no source and no destination should be marked as global input or output nets. This can be done using mark_global_input_net and mark_global_output_net and can be reversed using unmark_global_input_net and unmark_global_output_net. The current status of a net in that regard can be checked using is_global_input_net and is_global_output_net.

net = netlist.get_net_by_id(3)   # get net with ID 3
net.mark_global_input_net()      # mark net as global input net
net.is_global_input_net()        # return True
net.unmark_global_input_net()    # unmark net

By providing the net as input, all these functions can also be executed on the netlist itself. In addition, calling get_global_input_nets or get_global_output_nets on the netlist returns a list of all global input or output nets respectively.

net = netlist.get_net_by_id(3)         # get net with ID 3
netlist.mark_global_input_net(net)     # mark net as global input net
netlist.is_global_input_net(net)       # return True
netlist.unmark_global_input_net(net)   # unmark net
netlist.get_global_output_nets()       # return all global output nets