net − format of .net files read/written by Magic’s netlist editor
Netlist files are read and written by Magic’s netlist editor in a very simple ASCII format. The first line contains the characters ‘‘ Netlist File’’ (the leading blank is important). After that comes a blank line and then the descriptions of one or more nets. Each net contains one or more lines, where each line contains a single terminal name. The nets are separated by blank lines. Any line that is blank or whose first character is blank is considered to be a separator line and the rest of its contents are ignored.
Each terminal name is a path, much like a file path name in Unix. It consists of one or more fields separated by slashes. The last field in the path is the name of a label in a cell. The other fields (if any), are cell instance identifiers that form a path from the edit cell down to the label. The first instance identifier must name a subcell of the edit cell, the second must be a subcell of the first, and so on.
Instance identifiers are unique within their parent cells, so a terminal path selects a unique cell to contain the label. However, the same label may appear multiple times within its cell. When this occurs, Magic assumes that the identical labels identify electrically equivalent terminals; it will choose the closest of them when routing to that terminal. Further, after connecting to one of these terminals Magic may take advantage of the internal wiring connecting them together and route through a cell to complete the net’s wiring.
An example netlist file follows below. It contains three distinct nets. ———————————————————————————————————————
Netlist File
alu/bit_1/cout
alu/bit_2/cin
regcell[21,2]/output
latch[2]/input
This line starts with a blank, so it’s a separator.
opcode_pla/out6
shifter/drivers/shift2
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magic(1)