74LS192 Synchronous up/down decade counter
The 74LS192 counts in BCD, 0 to 9, up or down. It has two clocks: a rising edge on UP counts up while DOWN is held high, and a rising edge on DOWN counts down while UP is held high. It can load a value from A–D, and CLR, which is active-high, clears it.
74LS192 pinout
Top view of the 16-pin DIP package. Pin 1 is at the bottom left, beside the notch, and the numbers run anticlockwise. Power is on pin 16 (VCC, +5 V) and pin 8 (GND).
| Pin | Name | Type | What it is |
|---|---|---|---|
| 1 | B | Input | Input |
| 2 | QB | Output | Totem-pole output |
| 3 | QA | Output | Totem-pole output |
| 4 | DOWN | Input | Input |
| 5 | UP | Input | Input |
| 6 | QC | Output | Totem-pole output |
| 7 | QD | Output | Totem-pole output |
| 8 | GND | Ground | 0 V |
| 9 | D | Input | Input |
| 10 | C | Input | Input |
| 11 | LOAD′ | Input | Input, active-low |
| 12 | CO′ | Output | Totem-pole output, active-low |
| 13 | BO′ | Output | Totem-pole output, active-low |
| 14 | CLR | Input | Input |
| 15 | A | Input | Input |
| 16 | VCC | Power | +5 V supply |
74LS192 function table
| CLR | LOAD′ | UP | DOWN | What happens |
|---|---|---|---|---|
| 1 | X | X | X | Clear to 0 |
| 0 | 0 | X | X | Load A–D |
| 0 | 1 | ↑ | 1 | Count up |
| 0 | 1 | 1 | ↑ | Count down |
| 0 | 1 | 1 | 1 | Hold |
CO′, the carry out, pulses low as the count passes 9 going up; BO′, the borrow out, pulses low as it passes 0 going down. Connect them to UP and DOWN of the next counter.
What the 74LS192 is used for
- Up/down counters for a 7-segment display
- Countdown timers that start from a loaded value
- Multi-digit counters, chained through CO′ and BO′
Electrical summary
| Package | 16-pin DIP |
| Supply voltage | 5 V (4.75 V to 5.25 V) |
| Output type | Totem-pole — drives both high and low |
| Output current, low | sinks up to 8 mA |
| Output current, high | sources up to 0.4 mA |
| Input current, low | 0.4 mA out of each input held low |
| Fan-out | one output can drive about 20 LS inputs |
Typical figures for quick reference when planning a board. Check the manufacturer's datasheet for limits and timing before committing a design. The 74HC192 and 74HCT192 use the same pin numbers, with different electrical values.
The 74LS192 and the Breadboard Simulator
The 74LS192 is not in the Breadboard Simulator's parts library yet — this page is a reference. The simulator seats the gates, decoders, multiplexers, adders and buffers marked on the chips page, so the logic around a 74LS192 can be planned and wired there.