Omron register

shane_bac · Mar 4, 2015

Hi, i have created a sequence of steps in CX one lite and everything is working fine. I need to create a table or a register so that if a button is pressed the sequence will index back one position. I have been told i may need to create an index table to register what step i am to achieve this. Also i will need to undo any steps that have happened in the previous step. Any help would be greatful please. I have used set/reset marker bit instructions to create the sequence.

gclshortt · Mar 4, 2015

I would use indirect addressing for this application.

http://accautomation.ca/here-is-a-method-that-is-helping-plc-programmers-to-program-faster/

In the Omron controllers you can use the DM area. You specify the indirect addressing by using *DM. Create a pointer for the input and output conditions and manipulate the pointers to go forward or backward in the sequence.

I have used this approach before in a tube bending machine.

Regards,
Garry
http://www.accautomation.ca

Sergei Troizky · Mar 4, 2015

Not clear how the sequencer is implemented.
Are the states coded as a value in a register?
Or they are bits? If yes, are these bits consecutive or randomly located?
Is it a fixed or variable sequence?

shane_bac · Mar 5, 2015

Hi, the steps are as non retentive memory bits in order.
Step 1 = 0.0
Step 2 = 0.1
Step 3 = 0.2
As each step is set it will reset the previous step. I have then used these steps to determine the outputs at the required time. e.g. if step 1 is high cylinder 1 will extend until the reed switch goes high this will set the next step which will reset that step.
I now need to be able to press a button to go back a step at any time. I have never used an index registers and have only programed in this way (as i was taught in my HNC).

shane_bac · Mar 5, 2015

This is a fixed sequence

gclshortt · Mar 5, 2015

http://accautomation.ca/building-a-plc-program-that-you-can-be-proud-of-part-2/

Take a look at the above link. This can be done with your application. Manipulating the pointers, you can go forward or backward.
Regards,
Garry
http://www.accautomation.ca

shane_bac · Mar 5, 2015

Hi, i am trying to implement my current sequence into a register.
Everytime a step is complete i will increment the pointer word, if the step back button goes high for one scan it dec the word by 1. With this i will need to undo any cylinder positions that have been moved by the previous step. With reference to the link, where does the V1000 come from?

mendonsy · Mar 5, 2015

Using a register works just fine. You can use the ++(590) instruction to increment the register and the --(592) instruction to decrement the register. A simple compare =(300) will allow you to select rungs to execute for each step.
I suggest you use @++ and @-- instructions to insure that your logic does not allow the pointer to cascade.

shane_bac · Mar 5, 2015

And i can use the memory bit of each step going high to incremnt the register?

mendonsy · Mar 5, 2015

You can use whatever logic is necessary to trigger the @++ or @-- instructions. There may also be conditions where you need to skip steps. In that case you can use a +(400) to add a value to your step register or -(410) to subtract a value.
It is a good idea to have a dedicated rung at the end of your program to range check the register value just to insure it never becomes a value that you are not prepared to handle. For example, if yu have ten steps then check to make sure that the register value is < 11.

shane_bac · Mar 5, 2015

What will the range check do if it was to become an unpredicted value? Will it move the register back to zero or just wait for a reset?

mendonsy · Mar 5, 2015

That depends on your logic of course, but generally it would be an alarm condition requiring the operation to be shut down.
Once you get the system running it should never occur, but while you are testing it can be a handy thing to have.

shane_bac · Mar 5, 2015

Thank you, i will implement this and see how i get on.

mendonsy · Mar 5, 2015

Here is an example of one way to use a step register. This is a startup sequencer for a waste treatment plant.

Str8jCkt · Mar 5, 2015

shane_bac as indeicated by the responses there are several ways to do a sequencer. Is this a fairly small program?
You could post a copy of the logic you started and I'm sure there are several people on here that could help you go down a road you will understand.
I have always found that the method of doing a sequencer seems to a preference. Form experience, that are several ways to get the same answer but some people can "read" and understand one method easier than another.

Omron register

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