counters
Download
Skip this Video
Download Presentation
Counters

Loading in 2 Seconds...

play fullscreen
1 / 24

Counters - PowerPoint PPT Presentation


  • 1135 Views
  • Uploaded on

Counters Photon Counting Chip (PCC) Picture of fuse using PCC Interest The Difference Engine (1872) was a general purpose mechanical calculator solving mathematical problems with up to 31 digit places of accuracy. Through the use of punch-cards, the Analytical Engine could be programmed

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Counters' - Audrey


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
counters
Counters

Photon Counting Chip (PCC)

Picture of fuse using PCC

CENT-113 Digital Electronics

interest
Interest
  • The Difference Engine (1872) was a general purpose mechanical calculator solving mathematical problems with up to 31 digit places of accuracy.
  • Through the use of punch-cards, the Analytical Engine could be programmed

CENT-113 Digital Electronics

counters general information
Counters General Information
  • Purpose: Counting events or periods of time or putting events in sequence.
  • Other functions: Dividing frequency, addressing, and serving as memory units.
  • Flip-Flops are wired together forming circuits that count.
  • Self contained counters in ICs are available in TTL and CMOS.

CENT-113 Digital Electronics

ripple counters
Ripple Counters
  • 4-bit counter: D-C-B-A=8s-4s-2s-1s
    • 8s: Most Significant Digit/Bit (MSD/B)
    • 1s: Least Significant Digit/Bit (LSD/B)
    • BCD count from 0000 to 1111 (Decimal 0-15)
    • Need a counter with 16 different output states
      • Mod-16 counter: Modulus of the mod-16 counter undergoes 16 different states to complete the counting cycle.
      • Mod-16 counter uses 4 J-K flip-flops

CENT-113 Digital Electronics

mod 16 ripple counter

D

C

B

A

1

1

1

1

Q

Q

Q

Q

J

J

J

J

FF2

FF1

FF4

FF3

CLK

CLK

CLK

CLK

1

1

1

1

K

K

K

K

Mod-16 Ripple Counter

Clock Pulses

BinaryOutput

3

2

4

1

Input

Note: The clock triggers only FF1

-Mode 16 means the counter has 16 states.

-A ripple counter causes a chain reaction

change of FF states.

-asynchronous counter means that all FFs

do not trigger at The same time.

-4 bit counters have 4 binary outputs.

10

6

5

7

9

1

2

8

4

3

CLK

FF1 Q

FF2 Q

FF3 Q

FF4 Q

CENT-113 Digital Electronics

mod 10 ripple counter

1

1

1

Q

Q

Q

J

J

J

J

FF3

FF2

FF4

FF1

CLK

CLK

CLK

1

1

1

Mod-10 Ripple Counter
  • The counting sequence is 0000 to 1001 (0-9).
  • It has 4 places 8s, 4s, 2s, 1s
  • NAND gate clears all FF to 0 after the 1001 (9) count.
  • Also called a decade (meaning 10) counter.

Clock

Pulses

1

D

C

B

A

Q

CLK

K

K

K

K

1

CLR

CLR

CLR

CLR

CENT-113 Digital Electronics

synchronous counters
Synchronous Counters
  • A synchronous counter eliminates the accumulated propagation delay of the ripple counter by tying all clock inputs to a common clock signal.
  • In a synchronous counter each flip-flop must not be allowed to toggle until all flip-flops that precede it are high (set).
  • The J-K inputs are tied to an AND gate that ANDs the Q outputs from all previous flip-flops.
  • Synchronous counters can be used to form any modulus counter by using a NAND gate to reset all the flip-flops. The inputs to the logic gate are from the Q outputs of the flip-flops that form the binary representation of the MOD numbers.
  • Synchronous counters can be used as down counters by taking the output from the Q rather than the Q of each flip-flop.
  • Synchronous counters can be used in many of the same design applications as ripple counters.

CENT-113 Digital Electronics

3 bit mod 8 synchronous counter

1

Q

Q

J

J

J

FF3

FF2

FF1

CLK

CLK

1

K

K

3 Bit Mod 8 Synchronous Counter

Clock inputs are connected in parallel.

Used in high frequency operations.

J-K FFs used in toggle or hold modes.

Toggle: J=1, K=1 Hold J=0, K=0

C

B

A

Q

CLK

Clock

Pulses

K

Truth Table

CENT-113 Digital Electronics

questions
Questions
  • Q. What does it mean to be a 3 bit counter?
  • A. The maximum binary output is 111.
  • Q. What does it mean to be a Mod-7 counter?
  • A. There are seven unique counting states in the particular counter.
  • Q. What is the difference between a synchronous & an asynchronous counter when they both use clock inputs?
  • A. Most synchronous counters have parallel clocks.

CENT-113 Digital Electronics

3 bit ripple down counter

1

1

1

Q

Q

Q

J

J

J

FF1

FF2

FF3

CLK

CLK

CLK

1

1

1

K

K

K

Q

Q

Q

3 Bit Ripple Down Counter

Preset

Note: A counter that counts

higher to lower is called a

down counter. It recirculates

& goes back to 0111.

PS

C

B

A

PS

PS

Clock Pulses

Truth Table

CENT-113 Digital Electronics

self stopping counter

1

1

Q

Q

J

J

J

FF3

FF1

FF2

CLK

CLK

1

1

K

K

Q

Q

Q

Self-Stopping Counter
  • Up and down counters can be stopped by using a logic gate. The inputs to J & K at FF1 stops counter and places it in a hold, stopping count at 000.

Preset

PS

C

B

A

Q

PS

PS

Clock Pulses

CLK

K

CENT-113 Digital Electronics

counters as frequency dividers
Counters as Frequency Dividers

1 Second Timing Circuit

  • Counters are used for frequency division.
  • Uses: Digital clocks & watches, oscilloscopes, and television receivers.
  • A decade counter can be used as a divide by 10 counter. If a decade counter was used along with a mod-6 counter, the divide by 60 circuit would be designed.

Divide by

60 circuit

60 HZ

1 HZ ( 1 pulse per second)

CENT-113 Digital Electronics

ttl counters
TTL Counters
  • 7493 *182

CENT-113 Digital Electronics

synchronous up down counter ics
Synchronous Up/Down-Counter ICs
  • The 74192 is a BCD decade up/down synchronous counter.
  • The 74193 is a 4-bit binary up/down synchronous counter.
  • These chips have parallel data input leads used to preset the counter.
  • Two clock inputs are available. 1 UP count & another for a DOWN count.
  • A terminal count UP and a terminal count DOWN output signal can be used to cascade several ICs together.
  • Two additional synchronous IC counters are the 74190 and the 74191.
  • The 74190 is a BCD counter and the 74191 is a 4-bit binary counter.
  • These chips have a terminal count output and an enable input. With these two connections, cascaded ICs held-off until the proper count. This means that the entire counter can be synchronous.

CENT-113 Digital Electronics

cmos counters
CMOS Counters
  • 74HC393
  • 74HC193

CENT-113 Digital Electronics

74hc393 wired as 4 bit binary counter
74HC393 wired as 4-bit Binary Counter
  • Two 4-bit binary ripple counters, each counter has 4 T-FFs
  • MR input is an asynchronous master rest pin.
  • Triggered High to low.
  • Counts 0000 to 1111.

Q3

8s

4s

2s

1s

Q2

Clock

Pulses

Q1

Q0

CLK

Counter

74HC393

Reset

MR

Clear=1

Count=0

CENT-113 Digital Electronics

74hc193 wired as mod 6 counter

PL activates the synchronous parallel load

with a low just after the highest count of

Binary 0110.

+5V disables the CPD & ground disables MR.

PL

74HC193 wired as Mod-6 Counter
  • 74HC193 is a presettable synchronous 4-bit binary up/down counter IC
  • Clock edge triggered low to high.
  • Modes of operation: reset, parallel load, count up, count down

Q3

8s

4s

2s

1s

Q2

Q1

A

Q0

Counter

74HC193

B

C

D

+5V

Clock

Pulses

CPD

Count Down

CPU

Count Up

MR

CENT-113 Digital Electronics

counting system using optical encoder
Counting System using Optical Encoder

+5V

+5V

+5V

+5V

1

Optoisolator

4N25

4

Common

Anode

LED 1

+5V

Decade

Counter

74193

Decoder/Driver

7447

Count

Up

7414

2

2N3904NPN

3

CLR

GND

GND

CENT-113 Digital Electronics

74hc85 comparator ic
74HC85 Comparator IC
  • The 74HC/HCT85 are high-speed CMOS devices and are pin compatible with low power Schottky TTL (LSTTL).
  • The 74HC/HCT85 are 4-bit magnitude comparators that can be expanded to almost any length. They perform comparison of two 4-bit binary, BCD or other monotonic codes and present the three possible magnitude results at the outputs (QA>B, QA=B and QA<B). The 4-bit inputs are weighted (A0 to A3 and B0 to B3), where A3 and B3 are the most significant bits.

CENT-113 Digital Electronics

74hc85 comparator ic continued

L= Low logic level

H= High logic level

X= Don’t care

74HC85 Comparator IC Continued

Pin Diagram

Truth Diagram

Data Inputs

A3

B2

A2

A1

B1

A0

B0

Vcc

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

A>B

A=B

A<B

A>B

A=B

A<B

B3

GND

Data

Input

Cascade

Inputs

Outputs

-Two 4-bit comparators can be cascaded

to compare 8 bit numbers or words.

-Cascading means joined to another.

CENT-113 Digital Electronics

sequential logic troubleshooting tools
Sequential Logic Troubleshooting Tools
  • Commercial Logic Probe (TTL/CMOS SS) & (MEM/PULSE SS) In MEM any signal (0 or 1) can pulse (as short as 50ns) will activate the pulse LED.
  • Digital Logic Pulser: Lets you generate a signal.

CENT-113 Digital Electronics

sequential logic troubleshooting tools22
Sequential Logic Troubleshooting Tools
  • Logic monitors with IC clips check chips in circuits with each pin lit by LED.
  • Portable IC tester tests chips out of circuit.
  • Handheld Oscilloscope.

CENT-113 Digital Electronics

troubleshooting a counter
Troubleshooting a Counter
  • Use best tool.
  • Use 5 senses to troubleshoot.
  • Check powers supply and common.
  • Use logic monitor to observe counting operation.
  • Check reset.
  • Check bent pins

CENT-113 Digital Electronics

conclusions
Conclusions
  • A. What is the difference between a FF and a counting circuit?
  • Q. FFs are the building blocks for counting circuits.

CENT-113 Digital Electronics

ad