74LS90 DECADE BINARY COUNTER
The 7490 IC can be configured into different modes depending on the applications required. In it's most common mode, the 7490 is used as a general purpose decade counter, where only one of it's 10 lines is active at any given time. Sending in clock pulses into it's CLK input pin causes the currently active line to shut off and consequentially enables the next line in the sequence. After ten occurrences of this pattern, the device resets and line 0 starts the sequence over. By running one of the output lines into the reset pin, count sequences can be controlled to any length from one to ten.
This chip is suitable for chasing light circuits where only one light is one at a time. If counts of more than 10 are required, multiple 7490s can be cascaded, with suitable external controlling logic, to expand the sequence.
Other applications might include, sequence controllers, stepper motor controllers, microcontroller assisted display drivers, etc.