8.15基于VHDL硬件描述語言的基帶碼發(fā)生器程序設(shè)計(jì)與仿真見隨書所附光盤中文件：8.15基帶碼發(fā)生器VHDL程序與仿真。1．常用基帶碼發(fā)生器程序--文件名：HS_UJDM--功能：基于VHDL硬件描述語言，產(chǎn)生常用基帶碼--最后修改日期：2004.3.27libraryIEEE;useIEEE.STD_LOGIC_1164.ALL;useIEEE.STD_LOGIC_ARITH.ALL;useIEEE.STD_LOGIC_UNSIGNED.ALL;entityHS_UJDMisPort(clk:instd_logic;--系統(tǒng)時(shí)鐘 Start:instd_logic;--始能信號(hào) dat:instd_logic_vector(15downto0);--二進(jìn)制數(shù)據(jù)輸入端 NRZ:outstd_logic;--非歸零信號(hào)輸出端 DRZ:outstd_logic;--單極性歸零信號(hào)輸出端 SRZ:outstd_logic_vector(1downto0);--雙極性歸零信號(hào)輸出端 AMI:outstd_logic_vector(1downto0);--交替極性信號(hào)輸出端 CFM:outstd_logic;--差分信號(hào)輸出端 CMI:outstd_logic;--編碼信號(hào)反轉(zhuǎn)碼信號(hào)輸出端 FXM:outstd_logic);--分相碼（曼徹斯特碼）信號(hào)輸出端endHS_UJDM;architectureBehavioralofHS_UJDMisbeginprocess(clk,start)variablelatch_dat:std_logic_vector(15downto0);--十六位二進(jìn)制信號(hào)鎖存器variablelatch_sig:std_logic;--高位信號(hào)鎖存器variablelatch_cfm:std_logic;--差分碼信號(hào)寄存器variablelatch_cnt:std_logic;--基帶碼同步信號(hào)variablecount_fri:integerrange0to8; --分頻計(jì)數(shù)器（碼寬定義）variablecount_mov:integerrange0to16; --移位計(jì)數(shù)器beginifstart='0'thenlatch_cnt:='0';--異步復(fù)位latch_cfm:='0';latch_sig:='0';count_fri:=7;count_mov:=16;--異步置位latch_dat:="0000000000000000";elsifrising_edge(clk)thencount_fri:=count_fri+1;--分頻計(jì)數(shù)器+1ifcount_fri=8thencount_fri:=0;--計(jì)數(shù)到8 ifcount_mov<16thencount_mov:=count_mov+1;--移位計(jì)數(shù)器+1 latch_sig:=latch_dat(15);--二進(jìn)制碼高位移入latch_sig中 latch_dat:=latch_dat(14downto0)&'0';--二進(jìn)制數(shù)據(jù)向高位移動(dòng)一位，低位補(bǔ)零 elselatch_dat:=dat;count_mov:=0;--載入下一輪將發(fā)送的數(shù)據(jù)latch_cfm:='0';latch_sig:='0';latch_cnt:='0';--寄存器復(fù)位 endif;iflatch_sig='1'thenlatch_cfm:=not(latch_cfm);--差分碼信號(hào)寄存器中信號(hào)取反 endif; endif;ifcount_fri<4thenlatch_cnt:='1'; --基帶碼同步信號(hào)的占空比調(diào)節(jié)elselatch_cnt:='0';endif; endif;--碼形轉(zhuǎn)換部分 NRZ<=latch_sig;--非歸零碼信號(hào) DRZ<=latch_sigandlatch_cnt;--單極性歸零碼信號(hào) SRZ(0)<=latch_cnt;--雙極性歸零碼信號(hào) SRZ(1)<=not(latch_sig);--SRZ（1）=‘1’表示負(fù)極性 AMI(0)<=latch_sigandlatch_cnt;--極性交替碼信號(hào) AMI(1)<=not(latch_cfm);--AMI（1）=‘1’表示負(fù)極性 CFM<=latch_cfm;--差分碼信號(hào) FXM<=latch_cntxnorlatch_sig;--分相碼信號(hào) iflatch_sig='1'thenCMI<=latch_cfm;--編碼信號(hào)反轉(zhuǎn)碼 elseCMI<=not(latch_cnt); endif;endprocess;endBehavioral;2．常用基帶碼發(fā)生器程序仿真常用基帶碼時(shí)序仿真圖如圖8.15.7所示：（a）局部放大圖（b）全局仿真圖圖8.15.7常用基帶碼時(shí)序仿