Synchronous counter (74HC161)

Digital logic · Intermediate · about 15 minutes · part of Zen’s Electronics Design Mastery

In a synchronous counter every flip-flop shares one clock, and gates decide which bits toggle. All the bits change at the same instant: no ripple, no glitches. TC goes high at 15 so counters can be chained.

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How it works

Try it on the bench

1. Hold the LOAD button through a clock edge: the counter jumps to the preset (5 here, from switches 1 and 3).
2. Watch TC light for one count at F. Feed TC into a second counter’s CET to count to 255.
3. Make a decade (0–9) counter: preset 0 and load whenever the count reaches 9, using a NAND gate on Q3 and Q0.

Parts on the bench

• Bench power supply
• Clock / pulse generator
• DIP switch module
• 74xx161
• Hex display (decoded)
• Logic indicator LED
• Push button
• Resistor

In the course

Zen’s Electronics Design Mastery, module “Digital Electronics”.

More on digital logic

• AND gate
• OR gate
• NOT gate
• NAND gate
• NOR gate
• XOR gate
• NAND as a universal gate
• Half adder