CD74HC192

The 'HC192, 'HC193 and 'HCT193 are asynchronously presettable BCD Decade and Binary Up/Down synchronous counters, respectively.

Presetting the CD74HC192 counter to the number on the preset data inputs (P0-P3) is accomplished by a LOW asynchronous parallel load input (PL). The CD74HC192 counter is incremented on the low-to-high transition of the Clock-Up input (and a high level on the Clock- Down input) and decremented on the low to high transition of
the Clock-Down input (and a high level on the Clock-up input). A high level on the MR input overrides any other input to clear the counter to CD74HC192's zero state. The Terminal Count up (carry) goes low half a clock period before the zero count is reached and returns to a high level at the zero count. The Terminal Count Down (borrow) in the count down mode likewise goes low half a clock period before the CD74HC192 maximum count (9 in the 192 and 15 in the 193) and returns to high at the maximum count. Cascading is effected by connecting the carry and borrow outputs of a less significant counter to the Clock-Up and CLock-Down inputs, respectively, of the next most significant counter.

If a decade counter is present to an illegal state or assumes an illegal state when power is applied, CD74HC192 will return to the normal sequence in one count as shown in state diagram.