??? 摘? 要： 為了改善現(xiàn)有密碼輸入器容易造成密碼泄露的缺點(diǎn),，設(shè)計(jì)了保密型密碼輸入器,。闡述了保密型密碼輸入器的工作原理,，給出具體設(shè)計(jì)、計(jì)算機(jī)仿真,。經(jīng)過(guò)實(shí)驗(yàn)分析和計(jì)算機(jī)仿真,，該電路能夠最大限度地保護(hù)用戶密碼并且容易在工程中應(yīng)用。?

??? 關(guān)鍵詞： 密碼保護(hù),；鍵位,；仿真；VHDL?

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??? 在生活中人們?cè)絹?lái)越頻繁地使用各種各樣的密碼來(lái)管理私人信息和資金賬戶,。密碼作為個(gè)人信息的保密鎖,，在銀行、網(wǎng)絡(luò)等公共場(chǎng)合應(yīng)用廣泛,，普遍采用各種加密算法進(jìn)行處理,，有效地提高了安全可靠性。但是在一些場(chǎng)合，如ATM柜員機(jī),、商場(chǎng)刷卡消費(fèi)時(shí),，由于數(shù)字鍵盤排列具有一定的規(guī)律性，當(dāng)用戶輸入密碼時(shí),，即使旁人站在一米線以外,，也能通過(guò)輸入者手指的移動(dòng)順序猜出密碼，這使得原本安全可靠的密碼泄漏,，使密碼輸入器變得不再安全,。?

??? 目前國(guó)內(nèi)外對(duì)于密碼輸入器的改進(jìn)大都局限在外形設(shè)計(jì)上^[1]，如加罩,、將鍵盤方型布局改為V型等,，這些措施不能從根本上解決密碼泄漏問(wèn)題，并且給密碼輸入者帶來(lái)操作上的不便,。本文利用VHDL語(yǔ)言設(shè)計(jì)了一種新型保密型密碼輸入器,，使鍵盤上0～9的10個(gè)數(shù)字每次輸入時(shí)隨機(jī)排列，不再具有規(guī)律性,，從而使輸入密碼時(shí)手指按下的按鍵順序和目前普通的密碼輸入器按下的順序不同,，這樣就可以避免他人記下按鍵順序再根據(jù)鍵盤數(shù)字的排列規(guī)律猜出用戶輸入的密碼。?

1 設(shè)計(jì)思想?

??? 保密型密碼輸入器的最大特點(diǎn)就是它可以改變現(xiàn)有密碼輸入器鍵值排列順序,，在每一個(gè)按鍵上安裝一個(gè)數(shù)碼管,，每次輸入密碼時(shí)，0～9的鍵值隨機(jī)排列顯示,，同時(shí)還要完成以下功能：?

??? (1)產(chǎn)生0～9共10個(gè)隨機(jī)排列且不重復(fù)的數(shù)組,，用來(lái)確定鍵盤上數(shù)字的排列順序；?

??? (2)將隨機(jī)數(shù)組轉(zhuǎn)化成數(shù)碼管上要顯示的鍵值,，并順序輸出到相應(yīng)按鍵的數(shù)碼管上,；?

??? (3)對(duì)鍵盤進(jìn)行掃描，根據(jù)按下的鍵位信息與顯示到按鍵上的鍵值判斷出輸入的密碼,；?

??? (4)將密碼信息輸出,。?

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title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" 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title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路" title="分頻電路">分頻電路,、消除抖動(dòng)電路,、鍵盤譯碼電路、主體控制電路,。?

2 電路設(shè)計(jì)?

2.1 分頻電路?

??? 芯片中每一個(gè)模塊都要有一定的時(shí)鐘信號(hào)才能工作,，而且在外部鍵盤電路和動(dòng)態(tài)掃描數(shù)碼顯示管上都要加一定頻率的時(shí)鐘信號(hào)。利用分頻電路將從外部輸入的4 MHz的時(shí)鐘clk_4m經(jīng)過(guò)分頻后輸出各部分電路所需的時(shí)鐘脈沖,。在程序中設(shè)定一個(gè)20位的信號(hào)q,，在clk_4m到上升沿時(shí)q自加1,，這樣可以取q的其中幾位來(lái)達(dá)到分頻的目地。?

??? 頻率計(jì)算公式為：其中q(n)為從右起第n位信號(hào),。例如取q(1)即得到4分頻后的時(shí)鐘1 MHz,。?

??? 程序中各信號(hào)頻率為：信號(hào)clk_keyboard1是鍵盤行掃描信號(hào)，與鍵盤列掃描信號(hào)一同識(shí)別按鍵,，它的頻率設(shè)定為8 Hz,；信號(hào)clk_debounce是消除抖動(dòng)電路的采樣頻率，為128 Hz,。信號(hào)clk_disp1是數(shù)碼管掃描信號(hào),，它的頻率要高于人眼的最大可分辨頻率24 Hz，設(shè)定為128 Hz,。信號(hào)clk_scan是鍵盤的行掃描信號(hào),，一共有四位分別代表鍵盤上的四行，最低位clk_scan(0)代表第一行,，最高位clk_scan(3)代表第四行,，低電平有效，它與clk_keyboard1相對(duì)應(yīng),，即clk_keyboard1代表的二進(jìn)制數(shù),。?

2.2 消除抖動(dòng)電路?

??? 在輸入密碼時(shí)由于手抖動(dòng)或按鍵接觸時(shí)產(chǎn)生抖動(dòng)造成輸入信號(hào)不連續(xù)，利用消抖電路將信號(hào)變化成一個(gè)連續(xù)的信號(hào),，防止被誤認(rèn)為是多次輸入,。?

??? 以分頻電路輸入的消抖電路時(shí)鐘信號(hào)為采樣信號(hào)，檢查每個(gè)采樣信號(hào)的上升沿處輸入的信號(hào)key是什么狀態(tài),。當(dāng)key信號(hào)改變并且連續(xù)兩次采樣結(jié)果相同時(shí)才輸出改變后的信號(hào)dif_out,，否則將維持原來(lái)的輸出信號(hào)。?

??? 從圖1中可以看出,，key輸入多次的低電平,，模擬輸入時(shí)的抖動(dòng)。當(dāng)這些低電平的寬度未達(dá)到兩個(gè)上升沿的寬度時(shí),，輸出信號(hào)沒(méi)有改變；當(dāng)寬度超過(guò)兩個(gè)上升沿的寬度時(shí),，輸出信號(hào)才發(fā)生改變,，且輸出的低電平信號(hào)的寬度為一個(gè)采樣寬度。?

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圖1? 消除抖動(dòng)電路的仿真

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2.3 鍵盤譯碼電路?

??? 將鍵盤按鍵信息根據(jù)clk_keyboard1中0的位置判斷行位置,，根據(jù)信號(hào)c中0的位置判斷列位置,，從而確定按鍵位置，然后將這些鍵位的信息以四位二進(jìn)制碼的形式輸出,。?

??? 用clk_debounce1為觸發(fā)信號(hào),，每當(dāng)clk_debounce1在上升沿時(shí),，將clk_keyboard1和c合并送給內(nèi)部信號(hào)z，由程序判斷是哪一個(gè)鍵被按下,。flag_numb為輸出信號(hào)的標(biāo)記信號(hào),，它是在clk_debounce1的下降沿才變化，使得flag_numb信號(hào)比out_numb落后半個(gè)周期,。這樣確保在flag_numb信號(hào)為1時(shí),，輸出的out_numb信號(hào)是0～9中的一個(gè)。鍵盤掃描參數(shù)表由表1所示,。?

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??? 如圖2所示,，輸入0～9共10個(gè)按鍵信號(hào)，信號(hào)out_numb經(jīng)過(guò)譯碼后正確地輸出相應(yīng)按鍵,，并且flag_numb的上升沿位于out_numb信號(hào)的中間,，可完全確保flag_numb上升沿觸發(fā)寄存器移位存儲(chǔ)的都是out_numb有用的信號(hào)。?

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圖2? 鍵位譯碼電路的仿真

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2.4 主體控制電路?

??? 該部分電路的主要功能為產(chǎn)生隨機(jī)的數(shù)組,，用來(lái)確定S0～S9每個(gè)鍵位的鍵值,。定義10個(gè)信號(hào)a～j，將0～9 10個(gè)數(shù)分別賦值給a～j,，然后將a～j隨即排列組成一個(gè)數(shù)組,，排在第1位的將是在0號(hào)鍵位上顯示的數(shù)字，排在最后的將是在9號(hào)鍵位上顯示的數(shù)字,。表2定義了8個(gè)數(shù)組,，定義的數(shù)組越多鍵盤上數(shù)字顯示的變化種類就越多。另外定義一個(gè)s信號(hào),，當(dāng)開(kāi)始輸入密碼信號(hào)start有效時(shí),，s進(jìn)行累加，從而產(chǎn)生0～7的循環(huán),，用來(lái)選擇8個(gè)數(shù)組中的一個(gè),，進(jìn)而實(shí)現(xiàn)產(chǎn)生隨機(jī)數(shù)組的功能。?

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??? 當(dāng)start信號(hào)有效時(shí),，S經(jīng)過(guò)自加后就確定下來(lái),，選中一組隨機(jī)數(shù)組，程序就將數(shù)組的值保存起來(lái),，這個(gè)信號(hào)代表從0～9號(hào)鍵位的鍵值,。然后順序送到按鍵的數(shù)碼管顯示出來(lái)，例如s＝1時(shí),，S0～S9對(duì)應(yīng)數(shù)組behfadjgic,，即S0＝1，S1＝4,，S2＝7,，S3＝5,，……，S9＝2,。?

??? 程序中定義一個(gè)24位的二進(jìn)制信號(hào)acc作為寄存器用來(lái)存放6個(gè)密碼數(shù)字,，當(dāng)start有效就對(duì)寄存器清空(置1)和計(jì)數(shù)信號(hào)jishu置0。由鍵盤譯碼電路產(chǎn)生的標(biāo)志信號(hào)flag_numb的上升沿觸發(fā)寄存器向左移位,，把鍵位信號(hào)out_numb1從acc的最低位輸入,，并且每移一次計(jì)數(shù)信號(hào)jishu加1，這樣用戶輸入的前6位將被作為密碼保存在寄存器中,，超過(guò)六6位,，寄存器則不會(huì)記錄。?

??? 通過(guò)把寄存器acc中的鍵位信號(hào)和相應(yīng)的數(shù)組進(jìn)行對(duì)比,，就可以找出按鍵對(duì)應(yīng)的6位密碼(mima),，并可以將其輸出。?

??? 如圖3所示,，當(dāng)start信號(hào)有效使得s＝1時(shí),，按輸入信號(hào)的規(guī)則加入1～9這9個(gè)按鍵信號(hào)和flag_numb標(biāo)志信號(hào)?？梢钥闯鲈谳斎?～9這9個(gè)鍵后,，程序只存儲(chǔ)了前6個(gè)，由s=1推算出按下的1號(hào)～6號(hào)鍵位代表的密碼為475039,，這和仿真后輸出的結(jié)果一致,。?

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圖3? 控制電路的仿真

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2.5 頂層模塊的設(shè)計(jì)?

??? 各模塊利用VHDL語(yǔ)言設(shè)計(jì)，通過(guò)仿真,，功能都正確,，生成各自的功能符號(hào)，然后在MAX＋plusII平臺(tái)上利用原理圖設(shè)計(jì)方法調(diào)用各模塊,，將其按照電路原理連接在一起,，加上輸入、輸出信號(hào),，構(gòu)成的模塊圖如圖4所示,，由此可生成一個(gè)完整的程序。?

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圖4? 頂層模塊圖

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??? 本設(shè)計(jì)改變了傳統(tǒng)密碼輸入器的形式,，將每一個(gè)鍵所代表的數(shù)字進(jìn)行隨機(jī)排列,，防止用戶輸入密碼時(shí)被別人通過(guò)觀察手指移動(dòng)的位置而竊取密碼。并且該設(shè)計(jì)采用EPF10K10LC84－4芯片實(shí)現(xiàn),，外圍電路簡(jiǎn)單，工作穩(wěn)定可靠,，便于在銀行,、商場(chǎng)等工程中應(yīng)用,，并且作為內(nèi)蒙古大學(xué)本科生創(chuàng)新基金項(xiàng)目受到專家肯定。?

參考文獻(xiàn)?

[1] 李海波.銀行密碼輸入器改進(jìn)[J].青年科學(xué),，2005(3)：20-21.?

[2] 盧毅,，賴杰.VHDL與數(shù)字電路設(shè)計(jì)[M].北京：科學(xué)出版社，2001.?

[3] 潘松,，黃繼業(yè).EDA技術(shù)實(shí)用教程(第二版)[M].北京：科學(xué)出版社,，2005.?

[4] 褚振勇，翁木云.FPGA設(shè)計(jì)及應(yīng)用[M].西安：西安電子科技大學(xué)出版社,，2003.