# Counters - PowerPoint PPT Presentation

1 / 24

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

## Related searches for Counters

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

Counters

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 - - - - - - - - - - - - - - - - - - - - - - - - - -

### Counters

Photon Counting Chip (PCC)

Picture of fuse using PCC

CENT-113 Digital Electronics

### 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

• 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

• 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

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

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

• 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

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

• 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

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

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

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

• 7493 *182

CENT-113 Digital Electronics

### 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

• 74HC393

• 74HC193

CENT-113 Digital Electronics

### 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

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

+5V

+5V

+5V

+5V

1

Optoisolator

4N25

4

Common

Anode

LED 1

+5V

Counter

74193

Decoder/Driver

7447

Count

Up

7414

2

2N3904NPN

3

CLR

GND

GND

CENT-113 Digital Electronics

### 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

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

Inputs

Outputs

-Two 4-bit comparators can be cascaded

to compare 8 bit numbers or words.

CENT-113 Digital Electronics

### 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 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

• 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

• 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