ACT includes a static timing and power analysis engine called Cyclone. Cyclone takes an ACT design along with a Liberty file as well as (optional) parasitics to estimate the performance of the circuit, as well as to check any timing constraints required for correct operation.
Asynchronous circuits contain cycles of gates. How do we time them? The following provides more detail on how static timing analysis for asynchronous circuits works. Please read this before proceeding, as it will explain the terminology used as well as what the interact
commands below are for.
Note that timing analysis requires that the design has been mapped to cells.
The following two commands are used to read in the Liberty (.lib
) files for the cells in the design. The timer uses a Liberty file handle to refer to one complete set of characterized cells (at one corner). If your Liberty files are split into say one file per cell, then they can be merged into a single file handle using the commands below.
Command | Meaning |
---|---|
timer:lib-read <file> | This reads in the specified file name as a .lib Liberty file, which contains delay and power information for the cells used in the design. This returns a handle to the Liberty file, used in other timing commands to refer to the .lib . |
timer:lib-merge <lib> <file> | If your .lib file is split into multiple files (e.g. for different groups of cells), then this command can be used to combine them into one handle. <lib> is a valid Liberty file handle, and <file> is the new Liberty file to be merged into the file handle. |
There are two ways to create a timing graph:
ckt:cell-map
command), the timing arcs from each cell are computed from the production rules directly. These arcs are checked against the .lib
file, and an error is reported if the timing arc is missing from the .lib
..lib
file.
Delays and transition times are added to the timing graph using information in the .lib
file. Commands to read in .lib
files are:
Command | Meaning |
---|---|
timer:lib-read <file> | This command reads in a timing .lib file, and returns a handle. This handle is used to refer to the information from the lib file that was read by the timing engine. |
timer:lib-merge <lh> <file> | This command takes an existing lib handle <lh>, and adds the contents of the .lib file to the handle |