KEY Time borrowing is multistage, same-phase, single-cycle, and only affects setup slack.

Negative and Maximum Borrow Time

Negative borrow time = data arrival time - clock edge. A negative borrow time means no borrowing actually takes place.

Maximum borrow time = clock pulse width - library setup time. The latch's clock latency is also subtracted from the pulse width to get the true maximum borrow time.

KEY Negative borrow = arrival - clock edge; max borrow = pulse width - setup time - clock latency.

Rows in the Floorplan

Standard cells are placed in rows. All rows have equal height and spacing, though row width can vary. Cells in a row get power and ground from the VDD and VSS rails.

Some technologies allow rows to be flipped, so adjacent rows can share power and ground rails in a VDD-VSS-VDD pattern.

KEY Rows hold standard cells at equal height, flipped rows share VDD/VSS rails.

Magnetic Placement

Magnetic placement improves timing or congestion in a complex floorplan by marking fixed objects as 'magnets'; the tool then pulls their connected standard cells close to them. For best results, run magnetic placement before the standard cells are placed.

KEY Magnetic placement marks fixed objects as magnets so connected cells are pulled close to them.