SAIF & VCD Interoperability

To ensure seamless integration with existing industrial verification environments, Axiom produces standard IEEE 1364 Value Change Dump (.vcd) and Synopsys SAIF 2.0 (.saif) files.

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1. IEEE 1364 Value Change Dump (VCD)

Axiom's VcdWriter formats all netlist state transitions with standard VCD definitions:

• Header: $date, $version, $timescale 1 ps.
• Hierarchy: Hierarchical $scope module and $upscope blocks.
• Variables: Multi-bit $var wire [width] [symbol] [name] declarations.
• Initial Values: $dumpvars state dump at $t=0$.
• Transitions: Interleaved timestamp markers (#1000) with binary and hex bus transitions.

VCD files generated by Axiom can be opened directly in:

• GTKWave
• Surfer
• AMD Vivado Waveform Viewer
• Sigrok / PulseView

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2. Switching Activity Interchange Format (SAIF 2.0)

Accurate power estimation in Vivado's report_power requires high-confidence simulation vectors rather than static vectorless estimates.

Axiom produces valid SAIF 2.0 files containing switching probabilities:

(SAIFILE
  (SAIFVERSION "2.0")
  (DIRECTION "backward")
  (DESIGN "counter")
  (DATE "Axiom HDL Engine")
  (VENDOR "Axiom")
  (PROGRAM_NAME "Axiom Simulator")
  (PROGRAM_VERSION "0.1.0")
  (DIVIDER /)
  (TIMESCALE 1 ps)
  (DURATION 50000)
  (INSTANCE counter
    (NET
      (clk (T0 25000) (T1 25000) (TX 0) (TZ 0) (TC 99))
      (rst_n (T0 1000) (T1 49000) (TX 0) (TZ 0) (TC 1))
      (count (T0 12000) (T1 38000) (TX 0) (TZ 0) (TC 48))
    )
  )
)

Loading into AMD Vivado

In Vivado Tcl:

open_run impl_1
read_saif -strip_path /tb_top/u_dut -file power.saif
report_power -file post_sim_power.rpt

Vivado automatically updates its dynamic switching activity matrices from Axiom's measured SAIF toggle counts.