74LS163 Synchronous 4-bit binary counter, synchronous clear
The 74LS163 is the 74LS161 with one difference: its clear is synchronous, so CLR′ low resets the count on the next rising clock edge rather than at once. That makes it easy to build a counter that rolls over at any value without glitches.
74LS163 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 | CLR′ | Input | Input, active-low |
| 2 | CLK | Input | Input |
| 3 | A | Input | Input |
| 4 | B | Input | Input |
| 5 | C | Input | Input |
| 6 | D | Input | Input |
| 7 | ENP | Input | Input |
| 8 | GND | Ground | 0 V |
| 9 | LOAD′ | Input | Input, active-low |
| 10 | ENT | Input | Input |
| 11 | QD | Output | Totem-pole output |
| 12 | QC | Output | Totem-pole output |
| 13 | QB | Output | Totem-pole output |
| 14 | QA | Output | Totem-pole output |
| 15 | RCO | Output | Totem-pole output |
| 16 | VCC | Power | +5 V supply |
74LS163 function table
| CLR′ | LOAD′ | ENP | ENT | CLK | What happens |
|---|---|---|---|---|---|
| 0 | X | X | X | ↑ | Clear to 0 |
| 1 | 0 | X | X | ↑ | Load A–D |
| 1 | 1 | 1 | 1 | ↑ | Count up |
| 1 | 1 | 0 | X | X | Hold |
| 1 | 1 | X | 0 | X | Hold |
RCO, the ripple carry out, goes high while the count is 15 and ENT is high; it feeds ENT of the next counter to make a longer one.
What the 74LS163 is used for
- Counting to any modulus cleanly, by decoding the last count onto CLR′
- Synchronous counters and timers
- Counters of any length, chained through RCO and ENT
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 74HC163 and 74HCT163 use the same pin numbers, with different electrical values.
The 74LS163 and the Breadboard Simulator
The 74LS163 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 74LS163 can be planned and wired there.