Schematic diagram or circuit using 74LS193, 74LS76 mostly as IC's

use lm555 as clock

8.) Stopwatch with Multiplexing and Persistence of Vision Display .A stopwatch with a MM:SS display will continue to increment every second on stopped by the same external input. The display of the time will be connected to displays (or a single multi-digit 7-segment display) with common data input lines thus employing multiplexing and persistence of vision. four 7-segmen INPUT: 1 button to start and stop the time OUTPUTS: 7-segment display/s with 4 digits and common data inputs 8.) Stopwatch with Multiplexing and Persistence of Vision Display .A stopwatch with a MM:SS display will continue to increment every second on stopped by the same external input. The display of the time will be connected to displays (or a single multi-digit 7-segment display) with common data input lines thus employing multiplexing and persistence of vision. four 7-segmen INPUT: 1 button to start and stop the time OUTPUTS: 7-segment display/s with 4 digits and common data inputs