Your company here — click to reach over 10,000 unique daily visitors

netchange - Man Page

format of netchange files read by irsim.


A netchange file consists of a series of lines, each of which begins with a key letter. The key letter beginning a line determines how the remainder of the line is interpreted. The following are the list of key letters understood.

| any text

Lines beginning with a vertical bar are treated as comments and ignored by the program.

add type gate source drain length width [area]

Add a new transistor of type to the network. Currently, type may be:


n-channel enhancement transistor.


p-channel enhancement transistor.


depletion transistor (for NMOS).

The names of the nodes to which the gate, source, and drain of the transistor are connected are given by gate, source, and drain respectively. The length and width of the transistor are given by length and width respectively. The area parameter, if given, will use that number as the area for calculating the gate capacitance. Length and width should be given in lambda units, area should be in lambda 2 units, these will internally be multiplied by the LAMBDA factor from the configuration (.prm) file.

delete type gate source drain length width [area]

Delete an existing transistor from the net. All the parameters have the same meaning as for the add command.

move type gate source drain length width [area] g s d

Move an existing transistor to a new location the net. type, gate, source, drain, length, width, and area have the same meaning as for the add command. g, s, and d are the names of nodes to which the gate, source and drain should be connected.  If a particular terminal(s) is not to be re-connected, the name can be specified using an "*".  Any or all of g, s, and d may be "*".  For example, to move the gate of an n-channel transistor from node old to new the following command would be used:

m n old src_node drn_node 4 2.2 new * *

Note that the drain and source terminals, and the g and s terminals are interchangeable; the simulator will know if these are swapped.  So the last example could also have been written:

m n old drn_node src_node 4 2.2 new * *

capacitance node value

Change the capacitance of a node by value picofarads.   Value may be negative, thereby decreasing the node's capacitance. Node is the node name.

N node metal-area poly-area diff-area diff-perimeter

Change the capacitance of node using the area and perimeter information of the metal, polysilicon, and diffusion layers. All the parameters should be in lambda (or lambda 2 for areas) units, they will internally be converted to the appropriate capacitance as defined in the configuration file.  The values can be negative to decrease the capacitance.


Change the capacitance of node, using the following geometrical information:


area of 2nd-level metal


perimeter of 2nd-level metal


area of 1st-level metal


perimeter of 1st-level metal


area of polysilicon


perimeter of polysilicon


area of n-diffusion


perimeter of n-diffusion


area of p-diffusion


perimeter of p-diffusion

All perimeter values should be in lambda units, area values should be in lambda 2 units. The perimeter measures are half of the actual total perimeter (i.e., they are the sum of the lengths of the top and one side). Again, the values may be negative to decrease the capacitance of the node.

threshold node low high

Change the threhsold voltages of node. Low and high should be in normalized voltage units (i.e. floating-point numbers in the range 0.0 to 1.0).

Delay node tplh tphl

Change the delays for node to be tplh nanoseconds for low-to-high transistions, and tphl ns. for high-to-low transistions.  These should be absolute numbers, not relative increments/dercrements.


For all commands, only the first letter is significant, the rest of the string will be ignored.  They are only shown here for clarity.


This is an experimental interface for the incremental simulator and is very likely to change in the future.

See Also

irsim(5) sim(5) presim(1)

Referenced By


IRSIM User's Manual