Editing nets is started via 'create new net' in the library-menu or via hotkey 'n'. Nets are made by pairs of orthogonal lines. If you move the mouse after the first left-button mouseclick, you will see these two orthogonal lines. Clicking the left button fixes the last position of these two lines and gives you a new pair of lines. This way, you can draw a net containing as many pairs of lines as you want. The net editing is finished by clicking the right mouse button. If you want to change the edit style, use hotkeys 'h' and 'v'. 'v' means that the first line is drawn vertically, the second horizontally. 'h' means that the first line is drawn horizontally, the second vertically. If you have to draw a very long net, use hotkeys 's' and 'S' to snap the mouse to the next contact or net. 's' means the mouse is being warped to the next net or contact (whatever might be nearer to the actual mouse position). After warping, the program behaves as if you have hit the left mouse button: you will be able to continue net editing with two new lines. 'S' means that the mouse will be warped, and net editing will be finished at the snap position.
You should try 's' and 'S' in a dummy schematic before using it. If you hit 's' several times, and the mouse is warped to the same position every time, netparts of length zero would be created. Of course, this makes no sense, so, these netparts are removed . Every time this happens, an error message will appear on your xterm window like 'net rejected'. Don't worry, what you see on screen is what you get, so , if everything looks fine, it is okay.
The connectivity of schematics is defined by nets, global pins (gnd, vss,vdd,vss1, vdd1), named globals,
named pins, ports and symbol contacts.
Global pins and named globals may be placed on all hierarchy levels. However, it is necessary to
place each used global pin at least once on the top level.
For example, if you try to place voltage supply sources in a
symbol(schematic) on a deep hierarchy level and connect
it via global symbols to the rest of your schematic, you will receive
an error message.
You must place all global pins at least once on top level before
you can use them on lower levels. It is not allowed to use global pins
to connect sub-hierarchies with each other, bypassing the top
level.
Named pins and ports can also be placed in all levels, but unlike global pins, named pins and ports are local. Ports are used to define connectivity between different schematic levels. Named pins are used to define connectivity inside a single schematic sheet : nets which are attached to named pins of the same name are connected. Ports and pins are of the same object type: they are both of type 'pin'. So, you can use named pins instead of ports and ports instead of named pins. Users of SPICECAD versions < 1.7.4 know the concept of named pins, so, they do not need to change their hierarchical schematics if they do not want to do so. Users of SPICECAD versions >= 1.7.4 should use ports to define inter-sheet connectivity and named pins for intra-schemtic connectivity.
If you place a named pin in a schematic more than once,
nets on the current hierarchy level will be
connected to each other . This allows you to save space which you would need
otherwise for large nets running from one end of your schematic window
to the other, which looks quite ugly. If you have lost the overview of the
connectivity on a single schematic, you can use the 'highlight net' function
after netlisting.
This function is useful if you want to display a net when a net is split into many sub-nets which are connected by named pins , global pins, ports etc. Simply click at the net, and all sub-nets will be highlighted in yellow. Please do not forget to netlist before so that SPICECAD can determine the connectivity.