Digital counter
- 1. SEMINAR REPORT PRESENTATION ON DIGITAL COUNTER Presented by: BHASKAR KUMAR JHA Roll no.- 11900315014
- 2. Digital Counter Introduction Types of Digital Counter Asynchronous Counter Synchronous Counter Ring Counter Johnson Counter Application
- 3. A Digital counter is a sequential circuit consisting a set of flip-flops connected in a suitable manner to count the sequence of the input pulses presented to it in digital form. Counters can be broadly classified as follows: Asynchronous and synchronous counters Single and multi-mode counters Modulus counters Introduction
- 4. Asynchronous Counters Asynchronous Counter is one in which each flip flop is triggered by the output of the previous flip flop, which limits the speed of operation. Asynchronous counters are also called Ripple counter. These counters are easier to design and are constructed using minimum hardware.
- 5. Examples Designing of a Mod-8(3 bit) Asynchronous counter No. of flip flop depends on 2 𝑁 ≥ 𝐾 where N is number of flip flop & K is Mod no. ∴2n ≥ 8 n=3, i.e. 3 flip flop are required 𝐽0 𝑄0 𝑐𝑙𝑘0 𝐾0 𝑄0 𝐽1 𝑄1 𝑐𝑙𝑘1 𝐾1 𝑄1 𝐽2 𝑄2 𝑐𝑙𝑘2 𝐾2 𝑄2 1 1 1 𝑓𝑓0 𝑓𝑓2𝑓𝑓1 Clk
- 6. 𝑐𝑙𝑘0 𝑄0 𝑄1 𝑄2 000010001 011 111101 110100000𝑄2 𝑄1 𝑄0 It is also called Asynchronous up counter because it counts from 000 to 111. Timing Diagram
- 7. Asynchronous Down Counters 𝐽0 𝑄0 𝑐𝑙𝑘0 𝐾0 𝑄0 𝐽1 𝑄1 𝑐𝑙𝑘1 𝐾1 𝑄1 𝐽2 𝑄2 𝑐𝑙𝑘2 𝐾2 𝑄2 𝑓𝑓0 𝑓𝑓2𝑓𝑓1 Asynchronous Down Counter is one in which each flip flop is triggered by the inverse output of the previous flip flop. A down counter using n flip-flops downward from a maximum count of (2n-1) to zero. 1 1 1 Clk
- 8. 𝑐𝑙𝑘0 𝑄0 𝑄1 𝑄2 000110111 101 001011 010100000𝑄2 𝑄1 𝑄0 It is called Asynchronous Down counter because it counts from HIGH to LOW. Timing Diagram
- 9. Universal Asynchronous Counter 𝐽0 𝑄0 𝑐𝑙𝑘0 𝐾0 𝑄0 𝐽1 𝑄1 𝑐𝑙𝑘1 𝐾1 𝑄1 𝐽2 𝑄2 𝑐𝑙𝑘2 𝐾2 𝑄2 𝑓𝑓0 𝑓𝑓2𝑓𝑓1 1 11 𝑀 M The Universal counter is a combination of the up-counter and the down counter.
- 10. These problems can be eliminated by applying clock pulses to all the flip-flops simultaneously, which is done in a synchronous counter. Asynchronous counter Asynchronous counter is the simplest type of binary counters as it requires less hardware. But its speed of operation is low because the propagation delay time of all flip-flop is cumulative and the total settling time is the product of the total number of flip-flops and the propagation delay of a single flip-flop. Another problem encountered with asynchronous counter is the glitches at the decoding gate outputs.
- 11. Synchronous Counters In synchronous counters, the clock inputs of all the flip-flops are connected together and are triggered by the input pulses. Thus, all the flip-flops change state simultaneously (in parallel). Speed of operation is higher then Asynchronous counter.
- 12. Synchronous Counters Design Mod-4 Synchronous counter We know, 2n ≥ N ∴2n ≥ 4 n=2, i.e. 2 flip flop are required Qn Qn+1 J K 0 0 0 × 0 1 1 × 1 0 × 1 1 1 × 0 Count Value (Decimal) Count Value (Binary) Q1 Q0 𝑱 𝟏 𝑲 𝟏 𝑱 𝟎 𝑲 𝟎 0 0 0 0 × 1 × 1 0 1 1 × × 1 2 1 0 0 × 1 × 3 1 1 × 1 × 1 0 0 0 Excitation table
- 13. Q0 Q1 0 1 0 0 1 1 0 X K-map simplification Q0 Q1 0 1 0 1 X 1 1 X Q0 Q1 0 1 0 X 1 1 X 1 Q0 Q1 0 1 0 X X 1 X 1 For 𝐾1 For 𝐽0 For 𝐾0For 𝐽1 𝐽1 = 𝑄0 𝐾1=1 𝐽0=1 𝐾0=1 𝐽0 𝑄0 𝑐𝑙𝑘0 𝐾0 𝑄0 𝐽1 𝑄1 𝑐𝑙𝑘1 𝐾1 𝑄1 𝑓𝑓0 𝑓𝑓1 1 clock Clock Q1 Q0 0 0 0 1 1 0 1 1 0 0
- 14. Synchronous Universal Counters To form a synchronous universal counter, the control inputs are used to allow either the normal output or the inverted output of one flip- flop to the J and K inputs of the following flip-flop. 𝐽0 𝑄0 𝑐𝑙𝑘0 𝐾0 𝑄0 𝐽1 𝑄1 𝑐𝑙𝑘1 𝐾1 𝑄1 𝐽2 𝑄2 𝑐𝑙𝑘2 𝐾2 𝑄2 𝑓𝑓0 𝑓𝑓2𝑓𝑓1 1 Count-Down Clk Count-Up
- 15. Ring Counters The true output (Q) of the last flip-flop in a shift register is connected back to the first flip-flop. One flip-flop is set at any particular time while all others are cleared. A single 1 in the register is made to circulate around the register as long as clock pulses are applied, it is called a ring counter.
- 16. 𝐷0 𝑄0 𝑐𝑙𝑘0 𝑄0 𝐷1 𝑄1 𝑐𝑙𝑘1 𝑄1 𝐷2 𝑄2 𝑐𝑙𝑘2 𝑄2 𝑓𝑓0 𝑓𝑓2 𝑓𝑓1 𝑐𝑟 𝑝𝑟 𝑐𝑟 Clk 𝑂𝑅𝐼 ORI Clk Q0 Q1 Q2 L H H H X 1 0 0 0 1 0 0 0 1 1 0 0 No. of states= No. of flip flop Ring Counters
- 17. Johnson Counters The Johnson Counter is constructed similar to a standard ring counter except that the inverted output of the last flip-flop is connected to the input of the first flip-flop. 𝐷0 𝑄0 𝑐𝑙𝑘0 𝑄0 𝐷1 𝑄1 𝑐𝑙𝑘1 𝑄1 𝐷2 𝑄2 𝑐𝑙𝑘2 𝑄2 𝑓𝑓0 𝑓𝑓2 𝑓𝑓1 𝑐𝑟𝑐𝑟 𝑐𝑟 Clk ORI No. of states= 2 × No. of flip flop ORI Clk Q0 Q1 Q2 L H H H H H H X 0 0 0 1 0 0 1 1 0 1 1 1 0 1 1 0 0 1 0 0 0
- 18. Application: Some of their applications are : Tally Counter Digital Meter Product Counter Calculator
- 19. Thank you