通用串行总线(usb Universal Serial Bus)是一种计算机与外部设备连接的新技术，相对于PC传统的串/并行接口，USB具有较高的数据传输率、即插即用、热插拔、易扩充和低成本等优点。从USB标准颁布以来的短时间内，USB已成为PC必备的标准接口。
基于C51的usb信号发生器固件源代码。
SHOW FULL COLUMNS FROM `jrk_downrecords` [ RunTime:0.001056s ]
SELECT `a`.`aid`,`a`.`title`,`a`.`create_time`,`m`.`username` FROM `jrk_downrecords` `a` INNER JOIN `jrk_member` `m` ON `a`.`uid`=`m`.`id` WHERE `a`.`status` = 1 GROUP BY `a`.`aid` ORDER BY `a`.`create_time` DESC LIMIT 10 [ RunTime:0.067548s ]
SHOW FULL COLUMNS FROM `jrk_tagrecords` [ RunTime:0.001460s ]
SELECT * FROM `jrk_tagrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 20 [ RunTime:0.001413s ]
SHOW FULL COLUMNS FROM `jrk_member` [ RunTime:0.000988s ]
SELECT `id`,`username`,`userhead`,`usertime` FROM `jrk_member` WHERE `status` = 1 ORDER BY `usertime` DESC LIMIT 10 [ RunTime:0.004159s ]
SHOW FULL COLUMNS FROM `jrk_searchrecords` [ RunTime:0.001150s ]
SELECT * FROM `jrk_searchrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 5 [ RunTime:0.004040s ]
SELECT aid,title,count(aid) as c FROM `jrk_downrecords` GROUP BY `aid` ORDER BY `c` DESC LIMIT 10 [ RunTime:0.016708s ]
SHOW FULL COLUMNS FROM `jrk_articles` [ RunTime:0.001300s ]
UPDATE `jrk_articles` SET `hits` = 2 WHERE `id` = 454542 [ RunTime:0.016149s ]
