74C926 4-Digit Counter IC

The 74C926 CMOS counters have a 4-digit counter, an internal output latch, NPN output source drivers for a 7-segment display, and four multiplexing outputs. There is no need for an external clock because the multiplexing circuit has its own free-running oscillator. On the negative edge of the clock, the counters advance. The counter will be reset to zero and the carry-out will be reset to LOW if the Reset input is HIGH. The quantity within the counters will be latched into the interior output latches if the Latch Enable input is low. A HIGH signal on the Display Select input selects the amount to be displayed from the counter; a low level signal on the Display Select input selects the amount to be displayed from the output latch.

The MM74C925 is a 4-decade counter with inputs for Latch Enable, Clock, and Reset. The MM74C926 is similar to the MM74C925, except it has a display select and a carry-out for cascading counters. At 6000, the carry-out signal goes HIGH, then LOW at 0000. The MM74C927 is identical to the MM74C926 except that the second most important digit divides by 6 rather than 10. If the clock input frequency is 10 Hz, the display will show seconds and minutes in tenths of a second (i.e., 9:59.9).

The MM74C928 is identical to the MM74C926 except that the first significant figure divides by 2 instead of 10, and the carry-out is an overflow indicator that is HIGH at 2000 and returns to LOW only when the counter is reset. As a result, this is a 312 digit counter.