74LS290和74LS90都是二分频，五分频十进制计数器，功能相同，74LS290改变了引线排列。引线脚排列不同.
2018-01-26 10:09
The SN74LS90/SN74LS92/SN74LS93 are high-speed4-bit ripple type counters partitioned into two
2008-12-01 15:23
DM74LS90/DM74LS93Decade and Binary CountersGeneral DescriptionEach of these monolithic counters
2008-06-29 23:50
74LS90英文手册
2016-11-05 18:04
熟悉74ls90的引脚图、功能表，利用74ls90设计电子秒表
2016-05-20 16:50
74LS90 datashee—英版数据手册，感兴趣的可以看看哦。
2016-08-29 18:14
