2.四位二进制同步可异计数器74Ls193 CC a r QcB QcC LD C D 16 74LS193 B QB QA CPn CPu Qc QD1 8 16 9 74LS193 A B VCC QB QA CPD CPU QC QD QCB QCC Cr LD C D 2. 四位二进制同步可异计数器74LS193