The 74LS191 is a synchronous, reversible up/down counter having an inherent complexity of 58 equivalent gates. The 74LS191 is a 4-bit binary counter and the 74LS190 is a BCD counter. Synchronous operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincident with each other when so instructed by the steering logic. This mode of operation eliminates the output counting spikes normally associated with asynchronous (ripple clock) counters. The output of the IC always comes in TTL which makes it easy to work with other TTL devices and microcontrollers.
What is a Synchronous Binary Counter?
A Synchronous Binary Counter is a serial digital counter that counts ten digits. it resets for every new clock input. As it can go through 10 unique combinations of output, it is also called as “Decade counter”. A Synchronous binary counter can count 0000, 0001, 0010, 1000, 1001, 1010, 1011, 1110, 1111, 0000, and 0001 and so on. A 4 bit binary counter will act as a decade counter by skipping any six outputs out of the 16 (24) outputs.
74LS191 Key Features & Specifications
- Function: Counter
- Bits (#): 4
- Technology Family: LS
- VCC (Min): 4.75V
- VCC (Max): 5.25V
- Synchronous Counting
- Asynchronous Parallel Load
- Individual Preset Inputs
- Count Enable and Up/Down Control Inputs
- Cascadable
- Input type: TTL
- Output type: CMOS
74LS191 Pinout
| Pin No. | Pin Name | Description |
|---|---|---|
| 1 | B | Parallel Data Input B |
| 2 | QB | Flip Flop Output B |
| 3 | QA | Flip Flop Output A |
| 4 | CTEN’ | Clock Enable (Active Low) Input |
| 5 | D/U’ | Up/Down Count Control Input |
| 6 | QC | Flip Flop Output C |
| 7 | QD | Flip Flop Output D |
| 8 | GND | Ground Pin |
| 9 | D | Parallel Data Input D |
| 10 | C | Parallel Data Input C |
| 11 | LOAD’ | Parallel Load Control (Active Low) Input |
| 12 | MAX/MIN | Terminal Count Output |
| 13 | RCO’ | Ripple Clock Output |
| 14 | CLK | Clock Pulse Input |
| 15 | A | Parallel Data Input A |
| 16 | Vcc | Chip Supply Voltage |
Applications
The 74LS191 has a huge number of applications, a few of the are listed below:
- Astable frequency divider or counter circuit.
- Applications related to timing circuits.
74LS191 Datasheet
You can download the datasheet for 74LS191 Synchronous 4-Bit Up/Down Counter IC from the link given below:
See Also: 74LS139 Dual 1-Of-4 Decoder/Demultiplexer IC – Datasheet | 74LS83 4-Bit Binary Full Adder IC With Fast Carry – Datasheet | 74LS47 BCD to 7-Segment Display Decoder IC – Datasheet
