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Node Property: Property number 10

The node property defines a connection point of the device. It appears in device cell definitions and instance references.

5 10 circuit_node device_node x y [name phys_x phys_y] {flags lname refname};

The circuit_node is always set to -1 in the device library file. The device_node is a count, starting at zero, of the nodes assigned to the device or subcircuit. The node properties for a cell definition and its instances must share the same device_node's, i.e., there must be a one to one correspondence between listings (Xic maintains this). Device node zero is the reference node. When the device is placed in a drawing, the location of the reference node corresponds to where the user clicks. The device node numbers should be sequential and unique, and as mentioned start with zero. The x and y parameters specify the location of the terminal in database coordinates relative to the device cell origin. The default grid spacing is 1 micron (this is a vestige of the physical mode of Xic), thus it is advisable to place nodes at coordinates divisible by the resolution, which is 100 unless specified otherwise. The typical device in the library has a maximum dimension corresponding to 10 microns. The origin of the cell is arbitrary, the node locations should match the geometry of the cell.

If the node property is applied to a cell definition rather than an instance, and the device or subcircuit has a symbolic representation, the x and y parameters are of the form

x:syx y:syy
i.e., two fields of two numbers separated by colons. The first numbers of the two fields (x, y) are the coordinates of the terminal in the schematic representation. The second two numbers (syx, syy) are the coordinates of the terminal in the symbolic representation.

The bracketed quantities are optional, and are used by the netlist extraction subsystem. The name is a short identifying name given to the node, which should be unique among the nodes of a device or subcircuit. The next two parameters are the coordinates in the physical cell where the node is referenced, and should always be set to 0 in the device library file. If these three parameters are given, the device terminal is expected to have an actual physical location, meaning that the device is a ``real'' device, such as a resistor, rather than a simulation model such as a voltage source.

It is not necessarily true that all nodes of the device either have or don't have the optional parameters given in a device library file. The phase node of a Josephson junction, for example, does not have the parameters given, since this node has no physical counterpart. The other two nodes do have the optional parameters given, since these are the physical connection points. A side-effect is that in SPICE files created from physical data only the two nodes will appear in the device instantiation lines. This is acceptable to WRspice, since the phase node is optional.

If a device has no nodes with the optional parameters given, then it can never have a physical counterpart. The nophys property (described below) should also be given in that case.

If the bracketed parameters were given in the device library file, then instances of the device in symbol files may contain the last three fields. The flags field has the following bits possibly set:
bit 1 set if the terminal is not movable (unused)
bit 2 set if the terminal is virtual

The lname is the name of the layer to which the physical terminal is attached. It is the layer name from the technology file of a physical layer which has the Conductor attribute.

The refname is an optional keyword that specifies a terminal type. Valid keywords are:

input (default)
output
inout
tristate
clock
outclock
supply
outsupply
ground


next up previous contents index
Next: Name Property: Property Number Up: Device Properties Set By Previous: Device Properties Set By   Contents   Index
Stephen R. Whiteley 2006-10-23