The access to the data memory is different to each PLC. There are many marks and models of PLC. Some popular marks are Allen Bradley, Siemens, schneider-electric, Omron, Automation Direct among other. It is very difficult to talk about to access the processor memory in general way, so, a specific processor was chosen. The choice is a popular mark, that also it has free programming software and emulator. The result was Micrologix 1100 of Allen Bradley. In the future it will talk about others marks of PLC.
The micrologix 1100 has included I/O and also supports till 4 expansion modules. In total it can handle up to 144 digital I/O. It has RS-232/485 port, Ethernet port, 4k program memory, 4k data memory and LCD screen through which it can monitor and modify controller data. More details can be seen in the user manual.
Addressing data memory of the PLC
The PLC data memory is divided in files. Each file is of a specific data type. Nine default data files are created. These are:
- File 0, outputs (O0)
- File 1, inputs (I1)
- File 2, status (S2)
- File 3, binaries (B3)
- File 4, timers (T4)
- File 5, counters (C5)
- File 6, control registers (R6)
- File 7, de integers (N7)
- File 8, point floats (F8)
This memory distribution can be seen in RSLogixMicro.
Input and output address
The size of de output file is depending of the quantity of output modules in the PLC. For address of outputs, the format is as follows:
O:#output_module/#bit
Where #output_module is 0 for outputs on the base and 1, 2, 3 and 4 for output modules in the position 1, 2, 3 and 4 respectively, So, the address of the first output is O:0/0 and the address of the output 5 in the module on the position 3 is O:3/5.
The address of the input is very similar, just the “O” is changed for “I”. So, the address of the first input in the base is I:0/0 and the address of the input 6 in the module on the position 1 is I:1/6.
Binary and integer address.
Binaries and Integers are grouped in elements of 16 bits. The following format is used to address a bit: B3:#element/#bit or also B3/#bit, where the #element is omitted. In this sense, the address B3:1/1 and the address B3/17 are same, for example, like the next figure shows, in the position with the red x.
Bit address
Integers are of 16 bits, so, an integer can represent numbers in the range of -32.768 a 32.767. The address of the integers have the follows format: N:#elemento, so, a valid address for a integer is N7:1, referring to second integer of the file N7. Also it can access a particular bit of an integer, for example to access the last bit of the N7:1 the next address is used N7:1/15.
Timers and counter address
The address to access the timers, counters, control register, floating point and states will be explained later, when appropriate.
Instruction set of the PLC
The Micrologix 1100 controller is programming with ladder diagram. Instruction set of the processor is divided en group of instructions, such as: binary, timers and counters, arithmetic, logical, compare, program control among others.
Input and output instructions
Instructions that write on the data memory are called output instruction and are put in the last position on the rung. The rest of instructions are called input instructions.
Bit instruction group
The most basic instruction group is the binary and which we will explain below, within this group include the following instructions:
- Normally open contact (-] [-, XIC), input instruction. In this instruction is assigned a binary address, for example, an input (I), an output (O) or a bit (B) and its behavior is as a relay whose coil is the associated address. If the address state is 0 (false), then the contact is open and there is no logical continuity, in other words, the instruction is false. If the address state is 1 (true), then the contact will close and there is logical continuity between its ends, in other words, the instruction is true.
- Normally closed contact (-]/[-, XIO), input instruction. In this instruction is assigned a binary address, for example, an input (I), an output (O) or a bit (B) and its behavior is as a relay whose coil is the associated address. If the address state is 0 (false), then the contact is closed and there is logical continuity, in other words, the instruction is true. If the address state is 1 (true), then the contact will open and there is no logical continuity between its ends, in other words, the instruction is false.
- One shot (-[ONS]-, ONS), input instruction. In this instruction is assigned a bit (B) and always has, at least, one instruction before it. The ONS instruction checks the state of instructions before it. When the state changes from false to true (rising edge), the ONS instruction is true during the time of one scan cycle. The instruction is false the rest of time.
- Output coil (–( )–, OTE), output instruction. In this instruction is assigned a binary address, for example, an output (O) or a bit (B). When the rung is false, the OTE instruction writes 0 in the corresponding address and when the rung is true, the OTE instruction writes 1 in the corresponding address.
- Output latch (–(L)–, OTL), output instruction. In this instruction is assigned a binary address, for example, an output (O) or a bit (B). When the rung is false, the OTL instruction does not do anything and when the rung is true, the OTL instruction writes 1 in the corresponding address.
- Output unlatch (–(U)–, OTU), output instruction. In this instruction is assigned a binary address, for example, an output (O) or a bit (B). When the rung is false, the OTL instruction does not do anything and when the rung is true, the OTL instruction writes 0 in the corresponding address.
The complete instruction set of the PLC can be found here. The next figure shows the ladder diagram for a typical motor start developed with RSLogixMicro. A start button is connected in the input I:0/0, a stop button is connected in the input I:0/1, the auxiliary contact is connected in the input I:0/2 and the starter coil is connected in the output O:0/0. When the start button is pressed the rung is true till output instruction, then the starter is activated, the auxiliary contact is activated and the motor starts even if the start button is released. If stop button is pressed, the output instruction is false and the motor is stopped. The program can download to RSEmulate using RSLinx and then be tested.
PLC ladder diagram
Pingback: » PLC: mis primeros pasosControl Real
buy stromectol 12mg – candesartan 8mg over the counter carbamazepine for sale
order isotretinoin 10mg without prescription – zyvox 600mg cheap purchase linezolid
Looking forward to reading more. Great article.Really looking forward to read more.
WOW just what I was searching for. Came here by searching for tongkat ali supplementAlso visit my blog post thaipurchase.com
What’s up, just wanted to tell you, I liked this blog post.It was practical. Keep on posting!
Bardzo interesujące informacje! Idealnie to, czego szukałem! domowy generator tlenu domowy generator tlenu.
Heya i’m for the first time here. I came across this board and I in finding It really useful & it helped me out much.I’m hoping to offer one thing back and aid others suchas you aided me.
I really enjoy the blog.Much thanks again. Awesome.
Thank you for some other wonderful article. Where else could anyone get that type of information in such a perfect approach of writing? I’ve a presentation subsequent week, and I’m at the search for such information.
weaning off zoloft schedule sertraline effects
Greetings! Very useful advice in this particular article! It’s the little changes that produce the most significant changes. Thanks for sharing!
Amazing loads of valuable knowledge. phd thesis abstract what to write an essay about
Nice post. I was checking continuously this blog and I’m impressed!Very useful info specifically the last part 🙂 I care for such information much.I was looking for this particular info for a very long time.Thank you and good luck.
Well I really liked studying it. This tip offered by you is very useful for accurate planning.
Enjoyed every bit of your post.Much thanks again. Really Great.
Hey, thanks for the post.Really thank you! Want more.
Im obliged for the blog post.Thanks Again.
This is one awesome post.Much thanks again. Much obliged.
I value the post.Much thanks again. Awesome.
Thanks again for the blog article.Thanks Again. Really Great.
Thank you for your blog.Really looking forward to read more. Cool.
Pretty section of content. I just stumbled upon your blog and in accession capital to assert that I get actually enjoyed account your blog posts.Any way I will be subscribing to your augmentand even I achievement you access consistently quickly.
I think this is a real great article.Really looking forward to read more. Keep writing.
A fascinating discussion is worth comment. I do believe that you need to publish more on this subject matter, it might not be a taboo matter but usually people do not discuss these topics. To the next! Cheers.
Enjoyed every bit of your blog post.Really thank you! Want more.
Thông Tin, Sự Khiếu Nại Liên Quan Lại Đến Thẳng Soccer Nữ dangky.tluĐội tuyển Việt Nam chỉ cần thiết một kết quả hòa có bàn thắng để lần loại hai góp mặt tại World Cup futsal. Nhưng, để thực hiện được điều đó
Hey There. I found your blog using msn. That is a really well written article.I will make sure to bookmark it and come back to read more of your helpful information. Thank you forthe post. I’ll definitely comeback.
I really liked your post.Much thanks again. Really Cool.
Major thankies for the article post.Much thanks again. Really Great.
I value the article post.Much thanks again. Want more.
Amazing things here. I am very happy to peer your article.Thank you a lot and I’m having a look aheadto touch you. Will you kindly drop me a mail?
What’s up mates, its wonderful paragraph regarding cultureand fully defined, keep itup all the time.
zithromax where to buy – tinidazole 500mg pills order bystolic without prescription
Aw, this was a very nice post. In thought I wish to put in writing like this additionally taking time and precise effort to make a very good article however what can I say I procrastinate alot and in no way appear to get one thing done.
Hi there, I read your new stuff like every week. Your story-telling style is awesome, keep doing what you’redoing!
Hey there! I just wish to offer you a huge thumbs up for your great information you have here on this post. I will be returning to your blog for more soon.
A big thank you for your article.Really looking forward to read more. Will read on…
Hello.This article was really remarkable, especially since I was investigating for thoughts on this topic last Friday.
magnificent points altogether, you just won a new reader. What could you recommend in regards to your publish that you made some days in the past? Any certain?
Hi there, just became aware of your blog through Google, and found that it’s really informative. I am going to watch out for brussels. I will be grateful if you continue this in future. Lots of people will be benefited from your writing. Cheers!
buy prednisolone generic – cost omnacortil 40mg buy prometrium generic
the ridge apartments rentberry scam ico 30m$ raised doraville apartments
peptide liquid tadalafil elitenet tadalafil
I really liked your article. Want more.
Hi my loved one! I want to say that this article is awesome, nice written and come with almost all important infos. I?¦d like to peer more posts like this .
Major thanks for the blog post.Much thanks again. Really Great.
It¡¦s in reality a great and useful piece of info. I am satisfied that you just shared this useful info with us. Please keep us informed like this. Thank you for sharing.
I really enjoy the blog post. Want more.
Fine way of explaining, and good post to get data on the topic of my presentation subject, which i am goingto deliver in school.
Informative and precise Its difficult to find informative and precise info but here I found
I was suggested this blog by my cousin. I am not sure whether this post is written by him as noone else know such detailed about my difficulty.You are wonderful! Thanks!
Super-Duper blog! I am loving it!! Will be back later to read some more. I am bookmarking your feeds also
There may be noticeably a bundle to know about this. I assume you made sure nice points in features also.
metronidazole odontogenic infection flagyl nursing mother flagyl dose diverticulitis
buy gabapentin 100mg online – oral clomipramine 25mg order sporanox 100mg without prescription
how to use ivermectin for dogs ivermectin shampoo for head lice
Whats Happening i am new to this, I stumbled upon this I have found It absolutely helpful and it has aided me out loads. I hope to give a contribution & help other users like its aided me. Good job.
how to get furosemide without a prescription – betnovate 20 gm brand3 buy betamethasone 20 gm creams
pharmacy supply store near me walmart pharmacy camino canada
Really no matter if someone doesn’t understand afterward its up to other viewers thatthey will help, so here it occurs.
trustworthy canadian pharmacies turkey pharmacy online
buy monodox for sale – buy monodox sale how to get glipizide without a prescription
augmentin oral – augmentin oral duloxetine 20mg ca
I enjoy, cause I found exactly what I was taking a look for. You have ended my 4 day long hunt! God Bless you man. Have a nice day. Bye
This is one awesome post.Really looking forward to read more. Much obliged.
Thank you, I’ve just been looking for information about this topic for a while and yours is the best I have discovered till now. However, what concerning the bottom line? Are you sure about the source?
Thank you for sharing your thoughts. I trulyappreciate your efforts and I will be waiting for your next post thank you onceagain.
Thank you for your blog.Thanks Again. Will read on…
You have actually covered this topic professionally.
Thank you for your blog.Really looking forward to read more. Really Great.
accutane skin carestill breaking out on accutane month 5 accutane
Great post.
Hey there! I just wanted to ask if you ever have any issues with hackers? My last blog (wordpress) was hacked and I ended up losing months of hard work due to no back up. Do you have any solutions to protect against hackers?
A big thank you for your blog article.Thanks Again. Will read on…
Really appreciate you sharing this blog post. Great.
Very good blog.Thanks Again. Cool.
augmentin 1000mg pill – generic cymbalta 20mg cymbalta price
I loved your blog.Much thanks again. Great.
Hello! I know this is kinda off topic but I was wonderingif you knew where I could get a captcha plugin for my comment form?I’m using the same blog platform as yours and I’m having problems finding one?Thanks a lot!
Fascinating read and also the subject was good. Thank you with respect to preparing this commentary! I will be actually back with respect to more!
Thanks for sharing this fine article. Very interesting ideas! (as always, btw)
order rybelsus 14mg for sale – semaglutide cost buy generic periactin