Vec/Vcd/Evcd Digital Stimulus (vector)

Description

Spectre supports Digital Vector (VEC), Verilog-Value Change Dump (VCD), and Extended Verilog-Value Change Dump (EVCD).

VEC

To process digital vector files, the following command card needs to be specified in the netlist.

In Spice netlist:

.vec "vector_filename" [HLCheck = 0|1]

or

.vec vector_filename [HLCheck = 0|1]

Quotation marks can be double or single in Spice Netlist.

In Spectre netlist,

vec_include "vector_filename" [HLCheck = 0|1]

where,

vector_filename is the filename of the digital vector file.

HLCheck = 0 | 1 is a special flag (default = off) to create the vector output check for the H and L states of input signals. Bidirectional and output signals always check H and L states and are unaffected by the HLCheck flag.

Normally, you do not need to use the HLCheck flag.

Each command card specifies only one VEC file. If a netlist needs to include multiple VEC files, multiple.vec/vec_include cards must be used. For example, if a netlist contains three VEC files, it needs three .vec cards, as given below:

.vec "file1.vec"

.vec "file2.vec"

.vec "file3.vec"

VCD/EVCD

VCD and EVCD formats are widely used in digital circuit design and contain different kinds of information for transistor-level simulation. You need to provide signal information, such as timing characteristics, voltage threshold, and driving ability of input signals, for each VCD or EVCD file.

Because VCD and EVCD formats are compatible, the same signal information file can be shared between them.

The VCD file (ASCII format) contains information about value changes for selected variables in the circuit design. Spectre simulator supports two types of VCD files:

Four states - represents variable changes in 0, 1, x (unknown or not needed), and z (tri-state) without providing strength information and port direction.

Extended - represents variable changes in all states and provides strength information and port direction.

To process the VCD/EVCD file in Spectre, the following command card needs to be specified in the netlist.

In Spice netlist:

.vcd "vcd_filename" "signal_info_filename"

.evcd "evcd_filename" "signal_info_filename"

In Spectre netlist:

vcd_include  "vcd_filename" "signal_info_filename"

evcd_include "evcd_filename" "signal_info_filename"

Each command card specifies only one VCD file. If a netlist needs to include multiple VCD files, multiple.vcd/vcd_include cards must be used. For example, if a netlist contains three VCD files, it needs three.vcd cards, as given below:

.vcd "file1.vcd" "file1.signal"

.vcd "file2.vcd" "file2.signal"

.vcd "file3.vcd" "file3.signal"

Output Check

For VEC, VCD, and EVCD output check, the results are written in two files under the raw directory, one a check error report file %A.vecerr and the other a check summary report file %A.veclog where, %A is the analysis name.

To find VEC VCD and EVCD file, signal_info file format description and examples, refer to the Digital Vector File Format chapter in the Spectre Classic Simulator, Spectre APS, Spectre X, and Spectre XPS User Guide for details.

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