Often we are not concerned with a single operating condition, but a range of them. This can include manufacturing conditions (usually called "process"), temperatures, and voltages. Collectively, these are referred to as "PVT".
We are usually concerned with setup and hold times, which lead us to the idea of fast and slow corners. We want slow corners for setup times, because they will have the worst-case timing. We want fast corners for hold times, because they will have the best-case timing. However, it is difficult to predict what consistutes "fast" or "slow" for a given design. This is why multiple corners are used. Modern designs can have dozens or even hundreds of corners. We will illustrate with just a few in this tutorial which we will call "typical" (typ), "best case" (bc), and "worst case" (wc).
An entire
define_corners wc bc typ
read_lib -corner wc $env(PDK_ROOT)/sky130A/libs.ref/sky130_fd_sc_hd/lib/sky130_fd_sc_hd__ss_100C_1v60.lib
read_lib -corner bc $env(PDK_ROOT)/sky130A/libs.ref/sky130_fd_sc_hd/lib/sky130_fd_sc_hd__nom_n40C_1v95.lib
fead_lib -corner typ $env(PDK_ROOT)/sky130A/libs.ref/sky130_fd_sc_hd/lib/sky130_fd_sc_hd__tt_025C_1v80.lib
read_db odb/spm.db
read_spef -corner wc spef/max/spm.max.spef
read_spef -corner bc spef/max/spm.min.spef
read_spef -corner typ spef/max/spm.nom.spef
read_sdc sdc/spm.sdc
report_checksreport_checks -corner wc
report_checks -corner bc
report_checks -corner typCopyright 2024 VLSI-DA (see LICENSE for use)