54LS/74LS90中文资料ETC数据手册PDF规格书

DESCRIPTION — The ’90 is a 4-stage ripple counter containing a high speed

flip-flop acting as a divide-by-two and three flip-flops connected as a divideby-

five counter. It can be connected to operate with a conventional BCD output

pattern or it can be connected to provide a 50 duty cycle output. In the

BCD mode, HIGH signals on the Master Set (MS) inputs set the outputs to

BCD nine. HIGH signals on the Master Reset (MR) inputs force all outputs

LOW. For a similar counter with corner power pins, see the ’LS290; for dual

versions, see the ’LS390 and ’LS490.