VHDL4*4键盘按键循环显示

1）输入设备为4*4矩阵键盘，分别代表0~F； 2）输出设备为四位数码显示管，初始值显示0000，当按下某一键时，最右边的一位数码显示管显示最新一次所按按键的数值，而之前的显示值左移，例如，第一次按‘1’键，则显示0001；第二次按‘3’键，则显示0013；第三次按‘5’键，则显示0135；第四次按‘7’键，则显示1357；第五次按‘9’键，则显示3579，第四次按‘F’键，则显示579F等等；

 属性            大小     日期    时间   名称
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     文件        909  2009-04-10 20:05  SCAN_LED\SCAN_LED.qpf

     文件       1726  2009-04-10 20:17  SCAN_LED\SCAN_LED.qsf

     文件        137  2009-04-10 20:05  SCAN_LED\db\SCAN_LED.db_info

     文件       3221  2009-04-10 20:33  SCAN_LED\db\prev_cmp_SCAN_LED.sim.qmsg

     文件      15264  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.cmp.tdb

     文件      52443  2009-04-10 20:33  SCAN_LED\db\prev_cmp_SCAN_LED.qmsg

     文件         90  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.cbx.xml

     文件       5373  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.cmp0.ddb

     文件      18722  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.cmp.cdb

     文件       9546  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.cmp.hdb

     文件      16174  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.cmp.rdb

     文件       3221  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.sim.qmsg

     文件       2755  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.sim.hdb

     文件       1991  2009-04-10 21:21  SCAN_LED\db\SCAN_LED.sim.cvwf

     文件       3511  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.sim.rdb

     文件        154  2009-04-10 21:21  SCAN_LED\db\SCAN_LED.sld_design_entry.sci

     文件        161  2009-04-10 21:21  SCAN_LED\db\SCAN_LED.eco.cdb

     文件        784  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.hif

     文件       7109  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.hier_info

     文件          0  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.psp

     文件          0  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.pss

     文件          0  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.dbp

     文件          0  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.syn_hier_info

     文件          2  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.eds_overflow

     文件      11036  2009-04-10 21:21  SCAN_LED\db\wed.wsf

     文件       6328  2009-04-10 20:32  SCAN_LED\db\prev_cmp_SCAN_LED.map.qmsg

     文件       4555  2009-04-10 20:32  SCAN_LED\db\prev_cmp_SCAN_LED.fit.qmsg

     文件       1841  2009-04-10 20:32  SCAN_LED\db\prev_cmp_SCAN_LED.asm.qmsg

     文件      41075  2009-04-10 20:32  SCAN_LED\db\prev_cmp_SCAN_LED.tan.qmsg

     文件       6328  2009-04-10 20:33  SCAN_LED\db\SCAN_LED.map.qmsg

............此处省略41个文件信息