目前较为常用的串口有9针串口（DB9）和25针串口（DB25），通信距离较近时(<12m)，可以用电缆线直接连接标准RS232端口(RS422,RS485较远)，若距离较远，需附加调制解调器（MODEM）。最为简单且常用的是三线制接法，即地、接收数据和发送数据三脚相连，本文只涉及到最为基本的接法，且直接用RS232相连，以回答前段网友的咨询。-now more commonly used serial 9-pin serial port (projectors) and 25-pin serial port (DB25), Communication at close distance (
SHOW FULL COLUMNS FROM `jrk_downrecords` [ RunTime:0.001199s ]
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:0.090227s ]
SHOW FULL COLUMNS FROM `jrk_tagrecords` [ RunTime:0.001180s ]
SELECT * FROM `jrk_tagrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 20 [ RunTime:0.001937s ]
SHOW FULL COLUMNS FROM `jrk_member` [ RunTime:0.001159s ]
SELECT `id`,`username`,`userhead`,`usertime` FROM `jrk_member` WHERE `status` = 1 ORDER BY `usertime` DESC LIMIT 10 [ RunTime:0.003631s ]
SHOW FULL COLUMNS FROM `jrk_searchrecords` [ RunTime:0.000978s ]
SELECT * FROM `jrk_searchrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 5 [ RunTime:0.003325s ]
SELECT aid,title,count(aid) as c FROM `jrk_downrecords` GROUP BY `aid` ORDER BY `c` DESC LIMIT 10 [ RunTime:0.014929s ]
SHOW FULL COLUMNS FROM `jrk_articles` [ RunTime:0.001280s ]
UPDATE `jrk_articles` SET `hits` = 1 WHERE `id` = 137898 [ RunTime:0.001447s ]
