设计功能及要求 设计M=99的十进制加/减可逆计数器 （1）接通电源时电路能自启动； （2）手动分别实现加、减计数和自动实现加减可逆计数； （3）用数码管显示计数数值。 (4）给定元件：74LS192、74LS00、74LS76、74LS48及LED。

June 1989 54LS00/DM 74LS00 Quad 2-Input NAND Gates General Descr iption This device contains four independent gates each of which performs the logic NAND function. Features Y Alternate Military/Aerospace device (54LS00) is avail- able

74ls00资料，内有详細的说明，是做电路时很好的参考。74ls00 datasheet-74ls00 information, which is described in detail, is to do a good reference circuit. 74ls00 datasheet

74LS series data sheets