一段小程序，老是仿真出现问题如下：
Launching Application for process "Generate Expected Simulation Results".
Reading C:/Modeltech_5.7/tcl/vsim/pref.tcl
# 5.7
# do bb.ado
listening on address 127.0.0.1 port 1200
# ** Warning: (vlib-34) Library already exists at "work".
# resume
# Model Technology ModelSim SE vcom 5.7 Compiler 2002.12 Dec 18 2002
# -- Loading package standard
# -- Loading package std_logic_1164
# -- Loading package std_logic_arith
# -- Compiling entity i8051_dec
# -- Compiling architecture dfl of i8051_dec
# Model Technology ModelSim SE vlog 5.7 Compiler 2002.12 Dec 18 2002
# -- Compiling module bb
#
# Top level modules:
# bb
# vsim -lib work -t 1ps bb
# Attempting stack trace sig 11
# Signal caught: signo [11]
# vsim_stacktrace.vstf written
# Current time Thu Apr 13 14:53:23 2006
# ModelSim Stack Trace
# Program = vsim
# Id = "5.7"
# Version = "2002.12"
# Date = "Dec 19 2002"
# Platform = win32
# 0 0x004c6023: '<unknown (@0x4c6023)> + 0x20ff3'
# 1 0x004c5f4e: '<unknown (@0x4c5f4e)> + 0x20f1e'
# Corrupt Call Stack
# Loading work.bb
# Loading C:/Modeltech_5.7/win32/../std.standard
# Loading C:/Modeltech_5.7/win32/../ieee.std_logic_1164(body)
# Loading C:/Modeltech_5.7/win32/../ieee.std_logic_arith(body)
# Loading work.i8051_dec(dfl)
# ** Fatal: (SIGSEGV) Bad pointer access.
# Time: 0 ps Iteration: 0 Process: /bb/UUT/line__38 File: ../8051/8051/i8051_dec.vhd
# FATAL ERROR while loading design
# Error loading design
Error loading design
ERROR: VSim failed to simulate annotated testbench
源代码如下：
library IEEE;
use IEEE.STD_LOGIC_1164.all;
use IEEE.STD_LOGIC_ARITH.all;
entity i8051_dec is
port(
rst : in STD_LOGIC;
op_in : in UNSIGNED (7 downto 0);
op_out : out UNSIGNED (8 downto 0));
end i8051_dec;
-------------------------------------------------------------------------------
architecture DFL of i8051_dec is
begin
process(rst,op_in)
begin
if(rst='1') then
op_out<=("000000000" );
else
case op_in is
when "00010001"=>op_out <=("010000000" ) ;
when others=>op_out<="111111111" ;
-- ("00" & OPC_ERROR );
end case;
end if;
end process;
end DFL; | 
