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Monday, August 30, 2010

The Difference Between Parasitic Data Formats SPF, DSPF, RSPF, SPEF, and SBPF

Chapter 2: Parasitic Interconnect Corner (RC Corner)
2.1a 2.1b 2.2 2.3 2.4
Basics Of Capacitance and Resistance Interconnect Corners Interconnect Delay Models How to Read SPEF Difference between Parasitic Data Format

The acronyms stand for:
SPF--Standard Parasitic Format
DSPF--Detailed Standard Parasitic Format
RSPF--Reduced Standard Parasitic Format
SPEF--Standard Parasitic Exchange Format
SBPF -- Synopsys Binary Parasitic Format

SPF is a Cadence Design Systems standard for defining netlist parasitic. DSPF and RSPF are the two forms of SPF; the term SPF itself is sometimes used (or misused) to represent parasitic in general. DSPF and RSPF both represent parasitic information as an RC network.

RSPF represents each net as an RC "pi" model, which consists of an equivalent ”near" capacitance at the driver of the net, an equivalent "far" capacitance for the net, and an equivalent resistance connecting these two capacitances. Each net has a single "pi" network for the network, regardless of how many pins are on the net. In addition to the pi network, RSPF causes the PrimeTime tool to calculate an Elmore delay for every pin-to-pin interconnects delay.

In contrast, DSPF models a detailed network of RC parasitic for every net. DSPF is therefore more accurate than RSPF, but DPSF files can be an order of magnitude larger than RSPF files for the same design. In addition, there is no specification for coupling caps in DSPF. DSPF is more similar to a SPICE netlist than the other formats.

SPEF is an Open Verilog Initiative (OVI)--and now IEEE--format for defining netlist parasitic. SPEF is NOT identical to the SPF format, although it is used in a similar manner. Like the SPF format, SPEF includes resistance and capacitance parasitic. Also like the SPF format, SPEF can represent parasitic in detailed or reduced (pi-model) forms, with the reduced form probably being more commonly used. SPEF also has a syntax that allows the modeling of capacitance between different nets, so it is used by the PrimeTime SI (crosstalk) analysis tool. SPEF is smaller than SPF and DSPF because the names are mapped to integers to reduce file size.

SBPF is a Synopsys binary format supported by PrimeTime. Parasitic data converted to this format occupies less disk space and can be read much faster than the same data stored in SPEF format. You can convert parasitics to SBPF, by reading them in and then writing them out with the write_parasitics -format sbpf command.

Note: Reference From


  1. I just came to your post and reading above thing it is very impressive me and it is very nice blog. Thanks a lot for sharing this.

  2. As I know, the DSPF format can also have the specification for coupling capacitance on net.

  3. I think spef only has parasitics of wires not devices.
    The device power will be mentioned in .lib.
    Using .spef & .lib Prime-Time PX will calculate power. Correct me if I'm wrong.

    1. Hi,
      Are you talking about Device power or Device parasitic? In both the case these are not the part of SPEF.

  4. Good work, please keep writing!

  5. Difference between SDF and SPEF? can you explain please?

  6. Thank you for this sir! I have a question. We were tasked to design resistors and to check the highest parasitic capacitance and resistance in post sim. Do i have to check every capacitance value listed in the .sp file? Or are there capacitance values that i have to ignore?


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