Part Number: 7490
Function : Package Contains a Divide-by-Two and a Divide-by-Five Counter
Package: DIP 14 Pin Type
Manufacturer: National Semiconductor, ETC
Image and Pinout
Mode of operation
The device consists of 4 flip-flops which are connected internally to create one divide-by-2 and one divide-by-5 counters. All filp-flops have a common reset line controlled by two inputs MR1 and MR2. When both MR1 and MR2 are high the counters are cleared. Flip-flop 1 is not interally connected to the other stages, thus providing a variety of counter sequences :
a) Counting to 10 (BCD) : Output Q0 is connected to the Clock 1 input. The input pluses are applied to the Clock 0 input and the divided signal is extracted at Q3. The device counts in binary code up to 9, with the outputs returning to zero on the 10th clock pulse. Pins 2, 3 and 6, 7 must be grounded.
b) Divide by 2 and divide by 5 : Filp-flop 1 is used as a 2:1 divider and flip-flops 2, 3 and 4 are used as a 5:1 divider
Logic Diagram
