Johnson Counter | State diagram & Sequence table | Digital Systems Design | Lec-96

TL;DR

Johnson counters count clock pulses using a synchronous configuration with complemented flip-flop outputs.

Transcript

hi everyone in this video I'm going to explain about Johnson counter Johnson counter and previously we have discussed ring counter these two comes under these two come under uh synchronous counters that means all the flip flops how many number of bits we are using all the flip flops will be having a common clock pulse so that they will be synchrono... Read More

Key Insights

• 🔄 Johnson counters are categorized as synchronous counters, while ring counters are a different type, using direct outputs.
• 🐬 A key feature of Johnson counters is the connection of the last flip-flop's complemented output to the first flip-flop.
• 🔄 They require a common clock pulse to ensure all flip-flops operate synchronously, distinguishing them from asynchronous counter designs.
• 🐬 Each flip-flop in a Johnson counter only uses D-type flip-flops, simplifying the design.
• 🔄 The total count capability of a Johnson counter is based on the formula 2N, where N is the number of flip-flops.
• 🥺 Initial states of all flip-flops are typically set to zero, leading to predictable counting sequences.
• 🔄 The transition between states in Johnson counters is essential for understanding their sequential logic and output patterns.

Questions & Answers

Q: What is a Johnson counter, and how does it differ from a ring counter?

A Johnson counter is a type of synchronous counter that uses the complemented output of the last flip-flop as input for the first flip-flop, while in a ring counter, the output of the last flip-flop is connected directly to the first flip-flop without complementing.

Q: How many clock pulses can a Johnson counter with 4 bits count?

A 4-bit Johnson counter can count a total of 8 clock pulses, which is calculated by 2 times the number of bits, providing a unique capability compared to the ring counter that counts only 4 clock pulses.

Q: What role does the clock pulse play in a Johnson counter?

The clock pulse in a Johnson counter serves as a synchronous signal that activates all flip-flops simultaneously. When the clock pulse transitions, all flip-flops update their states based on input signals, maintaining synchronization throughout the counting process.

Q: Can you explain the state diagram of a Johnson counter?

The state diagram of a Johnson counter illustrates the progression of output states with each clock pulse. It outlines transitions such as from 0000 to 0001 up to 0111 and back to the initial state, clearly depicting how the counter cycles through its unique sequence.

Summary & Key Takeaways

• The video explains Johnson counters as a type of synchronous counter, contrasting them with ring counters that utilize standard output forms.

• A Johnson counter uses a complemented output from the last flip-flop as input to the first, allowing for a unique counting mechanism.

• The counter can handle up to 2N clock pulses, with N representing the number of bits or flip-flops used in the design.