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Digital Layout — Placement
Published in Louis Scheffer, Luciano Lavagno, Grant Martin, EDA for IC Implementation, Circuit Design, and Process Technology, 2018
A circuit netlist is composed of a number of components and a number of nets representing the required electrical connectivity between the various components, where a net connects two or more components. In the case of application specific integrated circuits (ASIC), the chip’s core layout area is comprised of a number of fixed height rows, with either some or no space between them. Each row consists of a number of sites which can be occupied by the circuit components. A free site is a site that is not occupied by any component. Circuit components are either standard cells, macro blocks, or I/O pads.* Standard cells have a fixed height equal to a row’s height, but have variable widths. The width of a cell is an integral number of sites. On the other hand, blocks are typically larger than cells and have variable heights that can stretch a multiple number of rows. Figure 5.2 gives a view of a typical placement layout. Blocks can have preassigned locations — say from a previous floorplanning process — which limit the placer’s task to assigning locations for just the cells. In this case, the blocks are typically referred to by fixed blocks. Alternatively, some or all of the blocks may not have preassigned locations. In this case, they have to be placed with the cells in what is commonly referred to as mixed-mode placement.
Computer-Based Circuit Simulation
Published in Jerry C. Whitaker, Electronic Systems Maintenance Handbook, 2017
To carry out a simulation, the circuit must first be described to the simulator. This is usually achieved using two methods: netlist and schematic capture. A netlist allows the user to describe a circuit using description statements, where each statement expresses a component or a signal source in terms of a name, node connections, and a value. The description statements are typed manually using a standard text editor, with the resulting file being called the circuit input file or the netlist. Because netlists are entered manually, it is easy for a user to make data entry mistakes; this problem increases over time as designs get larger. Schematic capture programs were introduced with the intention of simplifying the process of generating netlists. A schematic capture program allows a designer to draw a circuit using a mouse and symbols picked from the simulator library to represent the circuit. Once the circuit is drawn, the schematic capture program generates the circuit netlist automatically minimizing the input errors that occur when typing a netlist.
Introducing LTspice XVII Circuit Simulator
Published in Pooja Mohindru, Pankaj Mohindru, Electronic Circuit Analysis using LTspice XVII Simulator, 2021
Pooja Mohindru, Pankaj Mohindru
The schematic is a graphical interface to the circuit netlist generation, that is, the simulator interprets the circuit entered graphically on the schematic by a text netlist generated in the background. The netlist consists of a list of the circuit elements and their nodes, model definitions, and other SPICE commands. LTspice XVII saves schematic drafts with a file name extension of .asc. When a circuit drawn on the schematic is simulated, the netlist information is extracted from the schematic graphical information to a file with the same name as the schematic but with a file extension of .net.
Artificial neural network model for arrival time computation in gate level circuits
Published in Automatika, 2019
The arrival-time computation of the ISCAS-89 benchmark circuits using static timing analysis (STA) and statistical static timing analysis (SSTA) were performed. STA for circuits is described using the flow diagram shown in Figure 3 and the SSTA flow is illustrated in Figure 4. The Verilog file of the circuit must be given to the design compiler. This generates a netlist file for the circuit and a delay file in standard delay format (SDF). The netlist is a description of the connectivity of an electronic circuit. The SDF file contains the delay information for the gates and interconnects.