Is it not a mistake? Programming technique.

EStufC · Jan 20, 2020

hello,

Currently I'm playing with a module which has a command for getting its status. And I'm a bit puzzled by this picture which is provided by manufacturer. See attachment.

The question is, as per word mapping I should assign zeros only to bits 12,13,14.

However, what confuses me that if it is workable way "assignment zeros amid other not touched bits", I mean that anyway they (not touched) also have "zeros" by default.

In my opinion the module should not recognize a command. Actually what exactly we have right now.

Please any insigts on this matter?

Sydneyguy · Jan 20, 2020

Hi Buddy
I'm a little confused on what we are working with specifically, maybe you can shed some light for the rest of us forum members.
But if I am not mistaken, your asking how is it possible for a write command to only write to certain bits of a word. If your familiar with any allen bradley (simplest example) programming, that we often only write & read 'sampleword.bitnumber".

jstolaruk · Jan 20, 2020

Provide mfg and part number of the module, someone here has probably worked with it in the past and can help you out.

EStufC · Jan 20, 2020

jstolaruk said:
Provide mfg and part number of the module, someone here has probably worked with it in the past and can help you out.

This is OEM device, it has only,I suspect, a serial number.

Aabeck · Jan 20, 2020

When you want to read the status have a bit set.

Then, when that bit is on have 3 OTU (unlatch) outputs that turn off those 3 bits.

That will turn them off without effecting any of the other bits in the word.

EStufC · Jan 20, 2020

Aabeck said:
Then, when that bit is on have 3 OTU (unlatch) outputs that turn off those 3 bits.

How does this look like at code?

bernie_carlton · Jan 20, 2020

You will need to provide the PLC type and program language for any meaningful answer.

geniusintraining · Jan 20, 2020

EStufC said:
This is OEM device, it has only,I suspect, a serial number.

If they made their own odds are you will need to contact them, give us a screenshot of the software and maybe it will just be private labeled

EStufC · Jan 20, 2020

bernie_carlton said:
You will need to provide the PLC type and program language for any meaningful answer.

S7-300 series, it can be LAD, FBD or SCL.

EStufC · Jan 20, 2020

geniusintraining said:
If they made their own odds are you will need to contact them, give us a screenshot of the software and maybe it will just be private labeled

Frankly speaking, I can't get anything useful from manufacturer, due to unsufficient professionalism of those people who is in charge of support. I have strong feelings that I'm always speaking with moonlighting students which were applied by the company to perform some support. In other words we haven't any access to someone from developing of this company. Nowadays almost every company has similar organization, though.

mk42 · Jan 20, 2020

EStufC said:
S7-300 series, it can be LAD, FBD or SCL.

In the S7 world, if the command telegram to the device is at, say QW10, then you could turn off bits Q11.4, Q11.5, and Q11.6. In LAD, that could look something like this:







"Get Status"      Q11.4



-----||------------(R)

           |

           |       Q11.5



           |-------(R)

           |

           |       Q11.6



           |-------(R)

JesperMP · Jan 20, 2020

Can you tell us more about how you exchange data with the device ?
If the device in question is on Profibus, it is possible that it uses little-endian, whereas the S7 PLC uses big-endian. Maybe you have to swap bytes.

As you wrote in your 1st post it confuses you that you have to turn bits off to have diagnostics data. Yes, that sounds very odd.

parky · Jan 20, 2020

This sounds familiar, is the card a 6ES7090-0XX84-0FF5
if it is it's a coms card to connect a simovert drive

JesperMP · Jan 20, 2020

parky said:
This sounds familiar, is the card a 6ES7090-0XX84-0FF5
if it is it's a coms card to connect a simovert drive

Well spotted (if you are right about that).
If it is indeed a Siemens "PROFIBUS CBP2" for Simovert, then you definitely do not have to swap bytes.
There are a couple of FAQs, manuals and sample projects on Siemens support for that adapter.

EStufC · Jan 20, 2020

mk42 said:
In the S7 world, if the command telegram to the device is at, say QW10, then you could turn off bits Q11.4, Q11.5, and Q11.6. In LAD, that could look something like this:

Amid usage DPRD_DAT, MOVE_BLK and simple MOVE blocks to command this module, this simple LAD logic looks a bit rustic.

I've even tried masking words in a bid to achive some effect, but to no avail. Anyway I'll try that method.
As concerned byte representation it's being used Big Indian format, since I'm using the same module registers for different kind of commands and have no problems. The only one function is still defying, -Status.

if it was Siemens device, probably I would have decent support.

Is it not a mistake? Programming technique.

EStufC

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