User`s manual

A VCD file from source to output
ModelSim Xilinx User’s Manual Value Change Dump (VCD) Files 9-235
architecture RTL of SHIFTER_MOD is
begin
process (CLK,RESET)
begin
if (RESET = ’1’) then
Q <= (others => ’0’) ;
elsif (CLK’event and CLK = ’1’) then
Q <= Q(Q’left - 1 downto 0) & data_in ;
end if ;
end process ;
end ;
VCD simulator commands
At simulator time zero, the designer executes the following commands and quits
the simulator at time 1200:
vcd file output.vcd
vcd add -r *
force reset 1 0
force data_in 0 0
force clk 0 0
run 100
force clk 1 0, 0 50 -repeat 100
run 100
vcd off
force reset 0 0
force data_in 1 0
run 100
vcd on
run 850
force reset 1 0
run 50
vcd checkpoint
VCD output
The VCD file created as a result of the preceding scenario would be called
output.vcd. The following pages show how it would look.