As computers evolved from very

early transistor based models to the desktop personal

computers using microchips, memory and instruction registers

were 8 bits in length with computing, having to adapt to the

standard decimal based system. Specific instructions used

by programmers early on were designed with 8 bits in length

to facilitate all of computing and these instructions have been maintained

throughout the years of computer development and will most likely continue

to be used in the future. Within computers, each of the 8 bits have only two values for

representing either a logic “1” or True and a logic “0” or False. This is what is referred to as

Boolean in computer science. Boolean logic and expressions make the system of using binary

numbers perfect for use in digital or electronic circuits and systems. At RealPars, we love helping you learn so, if you enjoy this video as

much as we enjoyed making it, Click the like button. subscribe and click the bell and you’ll receive notifications

of new RealPars videos. so, you’ll never miss another one! The BCD system offers

relative ease of conversion between machine readable

and human readable numerals. An advantage of the Binary

Coded Decimal system is each decimal digit is denoted

by a group of 4 binary digits and that it allows easy

conversion between decimal a base 10 system and

binary a base 2 system. A disadvantage is BCD code does not

use all the states between binary 1010 for the decimal 10 and binary 1111 for the decimal 15. Binary coded decimal has specifically important

applications using digital displays. Now let’s talk about the binary

numbering system used in computers, this system is a Base 2 numbering system which follows the same set of rules used

with decimal or base 10 number system. Base 10 uses powers of ten, for example 1, 10, 100, 1000 and so on, where binary numbers use powers of two, effectively doubling the

value of each sequential bit, for example 1, 2, 4, 8, 16, 32 and so on. This conversion between

binary and decimal values is called Binary coded decimal and allows for easy conversion

between decimal and binary numbers. Binary coded decimal or BCD is a code

using a series of binary digits or bits that when decoded

represents a decimal digit. A decimal number contains 10

digits, zero to nine. So, each decimal digit 0 through 9 is represented by a

series of four binary bits where the numerical value when decoded

is equivalent to a decimal digit. In BCD we will use binary

numbers from 0000 to 1001, which are equivalent to decimal 0 to 9. Using the decimal number 5 for example, 5 in BCD is represented by 0101 and 2 in BCD is represented by 0010 and 15 in BCD is represented by 0001 0101. Let’s look a bit closer on

how this conversion works. The weighted binary coded decimal

representation of a decimal number and the comparison to the

decimal weighted representation. As we can see the decimal weight

of each decimal digit to the left increases by a factor of 10. With BCD number system, the binary weight of each digit

increases by a factor of 2. The first digit has a weight

of 1 or 2 to the power of 0, the second digit has a weight

of 2 or 2 to the power of 1, the third digit has a weight

of 4 or 2 to the power of 2, and the fourth digit has a weight

of 8 or 2 to the power of 3. Now with the basic understanding

of the binary weighted system, the relationship between decimal numbers

and weighted binary coded decimal digits for decimal values of 0 through 15 are provided as a truth table for BCD. Keep in mind, Binary coded decimal is not

the same as binary to decimal conversion. For example, if I would represent

the decimal number 72 in both forms, the bit formation would be like this: When we use a table to explain and expand

out the weighted values, using 16 bits, we can convert the

following decimal numbers: 9620, 120 and 4568 into

their binary equivalents. By adding together all

the decimal number values from right to left from each of the bit

positions that are represented by a “1” gives us the decimal equivalent. However, for the same decimal number, the BCD form representation

will be like this: 9620 equals this BCD value, 120 equals this BCD value, 4568 equals this BCD value. Electronic circuits and systems can

be divided into two types of circuits, analog and digital. Analog Circuits amplify

varying voltage levels that can alternate between a positive

and negative value over a period of time and Digital Circuits produce distinct

positive or negative voltage levels representing either a logic

level 1 or a logic level 0 state. Voltages used in digital

circuits could be any value, however in digital and computer

systems they are below 10 volts. In digital circuits voltages

are called logic levels and typically one voltage level

will represent a “HIGH” state, and the lower voltage level

will represent a “LOW” state. A binary number system will

use both of these two states. Digital signals consist

of discrete voltage levels that change between these

two “HIGH” and “LOW” states. BCD was commonly used for

displaying alpha-numeric in the past but in modern day BCD is still

used with real time clocks or RTC chips to keep

track of wall clock time and it’s becoming more common for embedded

microprocessors to include an RTC. It’s very common for RTCs to

store the time in BCD format. A binary clock might use LEDs

to express binary values. With this clock each column of LEDs

displays a binary coded decimal numeral. Back in the days, before touchscreens, seven segment displays,

and thumbwheel switches were used for a numerical

interface between PLCs and humans. Even before the PLC, these BCD type devices were the

only graphical way to interface with system circuits numerically. Some PLCs for example, Siemens S7

standard timer and counter data types use Binary Coded Decimal

in their data structures because these structures go back to

when engineers had to deal with things like these thumbwheels

and 7 segment displays. In fact, the S7 timer setpoints

are still entered as “S5T#2S” for a two second setpoint because this is inherited

from the S5 PLC platform. These timers use three BCD digits or 12 bits and two extra

bits for the time base. This is true for counters in which

they only count from 0 to +999. This concludes the video, “What is Binary Coded Decimal or BCD

and how is it used in Automation”. Here at RealPars our team

of experts is on hand to answer your questions

and respond to your feedback. If you’d like to learn more about any

of the topics covered in this video head over to our website at RealPars.com. We’d love to hear your suggestions

for topics you want our team to cover. Also, be sure to download the RealPars app. When you download the app, you’ll be able to watch an entire

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Great job sir

Good work and keep going you are doing great work…

Is it possible to have access to all videos by subscribing on the website or app? Because on the website, there are packs of videos with their specific price labels and it confuses me.

I'm not sure whether I should pay for packs or just subscribe.

Thank you for helping people who work out in the field

Please guys, do videos about simotion, profinet, profibus dp and pa…

This is really awesome! It is an easy topic, but because we sometimes mix up between decimal to BCD conversions and Decimal to Binary conversions, it seems challenging! This video really cleared it up. Thanks Real Pars

Awesome as always

Can we get something on CNC in automation? Sinumerik 840D sl etc.

Thank you Realpars for everything. Regards from Cancun Mexico…

BCD is used extensively in the OMRON CP and CJ series PLCs as well, in fact many of the instructions in CX-Programmer have a BCD and Binary version. Their more modern NJ/NX series use tag based data types that obscure the binary coding.

Thanks RealPars, great video

Is there a chance to teach us system architecture drawing?

Congrats on 400k subscribers!!!

Any video to show how to copy the programming file from PLC