Need of general hardware knowledge

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Mar 2018
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Hi

I am a beginner within the PLC world. But I want to learn as much as possible. So here are som questions based on the product information about Beckhoff's CX9020.

It runs with a Processor with these poroprties: ARM Cortex™-A8, 1 GHz. What does the abreviation ARM stand for? What is Cortex, other than a company and/or brand name? What does -A8 means?
1 GHz means 1 billion Hertz. But what does that figure correspond to in reality?

The information says that the number fo cores are 1. Is the core the same thing as the brain of the Central Processing Unit (CPU)?

What is a flash memory?
It says that its flash memory has these properties: 512 MB microSD (optionally expandable), 2 x microSD card slot

Are there any other types of flash memories than microSD wihtin the PLC world? If so, which are there?

It has an Internal main memory with 1 GB DDR3 RAM. What does 1 gigabyte correspond to in terms of plc programming rungs/commands/etc?
RAM is an abrevation för Random Access Memory, to the best of my knowledge. But what does DDR3 mean?

Its persistent memory is 128 KB NOVRAM integrated. What does 128 000 bytes correspond to in terms of plc programming? What does NOVRAM stand for?

Its interfaces are 2 x RJ45 (Ethernet, internal switch), 10/100 Mbit/s, DVI-D, 4 x USB 2.0, 1 x optional interface.
Ethernet is ordinary network cable. I also know what USB is. But what is DVI-D and 2 x RJ45?

Its I/O connection is E-bus or K-bus. What is a E-bus and a K-bus?
 
Personally I wouldn't worry so much about the hardware specs . . .
I'd worry about learning how to interface and write programs
for it and how to upload / download to it.

DVI sounds like a video connection - as in if one has a DVI monitor
(or perhaps HMI) one can plug it right into the PLC.

RJ45 is the name for the style Ethernet connectors. (Looks like an
eight wire telephone jack.)

Poet.
 
You guys have never put together a PC from parts, have you?

Sorry, could not help, don't want to sound arrogant, it is just a generational thing I guess. My dad used to build black-and-white TVs from parts - that was the skill well out of my reach :)
 
Mad_poet:
I can see your point in not fousing too much on the hardware. But I have programmed and been trouble shooting for more than one year in Omron, Rockwell, Siemens, Mitsubishi, ABB and some more in ST, LD, FBD. I got the basic skills of PLC programming covered. That is not the case regarding hardware.
 
No I hav never put together a PC. But I have high ambitions of learning a lot. Somewhere has to be the beginning. Mine is here.

You are asking a lot of good questions, but if you are just beginning then you may be getting ahead of yourself.r

As most of them seem to be hardware based, back up a little and make sure you are educated on the different types of I/O modules and when to use each type.

Also, the most advanced PLC and best written program won’t do a darn thing if the system always blows the main fuse because it is designed wrong.

Sensors, like photo eyes, prox. switches and analog transmitters are a huge part for whether the PLC system will do what you want. Same thing applies for output devices like solenoids and motor starters.

You have come to a great place to get good advice, just don’t let some of the responses get you down. Good luck.
 
This is to the best of my knowledge others might have more info:
You're going to see that most plc's and industrial equipment are going to have a form a microprocessor. 1GHZ CPU clock frequency is how fast the processor will execute commands what this means for us as end is that you are going to have a pretty fast plc scan time.

Flash memory is a type of non-volatile, non-volatile memory basically means that after you turn off the device and turn it back on the program is still there, a lot of really old machines are going to have plc's on them with volatile where the program was stored in RAM as an example if the on board battery died you would lose everything. Flash used to be pretty expensive and was sold as option card some of the ones I have seen are compact flash cards,on board chips(EEPROM), and USB(very rare on plc as flash).

DDR3 is a late 2000s style ram chip this will also determine scan time and how fast your plc execute math commands, I may be wrong about this but I think that DDR3 was the first type of ram to utilize both the positive edge and the negative edge for clock pulses.

RJ-45 is your common Ethernet communication port these are your common RJ45 ports. I don't know what they mean by "switched" could be auto switching or internal switch this I think will only apply if you trying to communicate from your computer directly to the processor in which you may have to use a cross over cable if it does not.

DVI-D as others have mentioned is a video connector for VGA type monitors, this means you can plug in a monitor directly into the plc, I don't know of another manufacture that does this here is what I found on the beck off site about this: https://www.beckhoff.com/english.asp?industrial_pc/cp_dvi.htm?id=451687892053394

NOVRAM is non volatile access memory so it remembers stored RAM values after power down, this means that even after battery(if it has one) failure your plc will remember the real time clock, where it was in the program(if you allow it to), ect.

I'm not to sure on the bus type.

I have never used a beckoff plc but I do know they use CODESYS for programming and i think is kind of a double edge sword to get started on programming a plc on one hand you have access to all the big IEC ladder, function block, structured text, ect. but on other because you have access to all the languages at once it can feel very overwhelming getting started just my opinion.
 
Last edited:
You guys have never put together a PC from parts, have you?

Sorry, could not help, don't want to sound arrogant, it is just a generational thing I guess. My dad used to build black-and-white TVs from parts - that was the skill well out of my reach :)
It is a generational thing. I put together plenty of PCs and one of the older guy here put together test system with nothing but some chips and assembly code. The new guys comes in and expect everything to be touch screen.

I do agree that time would be better spent on learn how to use the system rather than what the "gut" is made of though. However, I have to say, if you don't know what RJ45 or DVI means, then some basic computer/electronic knowledge (via search engine) would be highly recommended. In fact, these days, I would say one of the most valued skill is the google-fu.
 
I am a beginner within the PLC world. But I want to learn as much as possible. So here are som questions based on the product information about Beckhoff's CX9020.

I would have to agree with some of the other posters that these details aren't really what you need to be focusing on. I'll try to explain why as I go through your questions. A bit of googling and wikipedia would go a long way to finding these answers on your own. The moral of the story is that you probably aren't running your code directly on the PC hardware. The PLC firmware is running directly on the chip, and then your code runs on the PLC firmware.

The part you selected appears to also have the option to run a version of Windows in addition to the PLC runtime. That is why it lists all the PC specs. Normally, something like a DVI port wouldn't be relevant to a PLC.

ARM is a processor architecture, and also the name of the company responsible for designing/licensing it. A Processor archtiecture pretty much means how the chip is designed. ARM chips are typically used for low power/embedded devices. Windows computers use something else (x68, which became x64). Cortex is more or less a substyle of chip, and A8 is basically a model number. Most of the hot smartphones in 2010 (Iphone4, Nexus S, whatever samsung Galaxy S# they were at at the time) used this as their main processor.

1 GHz essentially means that the CPU executes instructions every 1 billionth of a second. HOWEVER, you are 2 layers removed from that cycle. The CPU is running the PLC firmware, which is then running the code you write. Your code is compiled down into any number of actual CPU instructions. Maybe something simple like addition is 4 instructions, but more complicated actions could take much longer to execute.

Some CPUs have multiple cores, which means it can run multiple threads in parallel. Most PLCs have 1 core, because your user program only does one thing at a time. Some PLCs have a separate core for things like communications.

Flash memory is a type of memory that doesn't lose its data when it loses power. SD cards are one common type of (removable) flash memory. They've gotten smaller over the years, regular SD to mini-SD to MicroSD. There used to be a ton of competing formats that looked the same (MMC, XSD, etc) but they have mostly died out. There is another kind of removable flash memory that is still common, which is CompactFlash. It is starting to be replaced by the much faster CFAST.

NVRAM (NOVRAM in their marketing) is another type of flash memory. The difference is that it isn't removable; it is soldered straight to the motherboard. This is typically used for retentive memory, and typically comes in smaller amounts than the removable cards. The direct mounting means that it can generally be accessed faster than the data on the removable flash cards.

What does this mean for your PLC? If all the NVRAM is for retentive memory 128KB is a fair bit. It depends on how much data your system can't afford to lose when power is gone.

DDR3 is just a type of RAM. There have been a ton of styles over the years, sometimes changing shape slightly, mostly different electrical characteristics. Mostly, there have been improvements to make it faster.

As others have mentioned, RJ45 is the name for the plug on your Ethernet cable. DVI is a display standard. DVI-D is digital only. It can be converted to HDMI, but not the older VGA (analog) connectors.
 

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