Nizami_225

Writing access to Safety CPU

9 posts in this topic

Hello.

I tried to read/write from/to safety cpu (QS001) over MC protocol. I managed to read from cpu devices but i couldn't write to any safety cpu device. It was possible to write data to Q series plc (Q02HCPU in my example) with MC protocol. I am searching any method of writing to safety cpu (QS001). If anyone could this before? And are there any settings in GX Developer (GX works) for access to writing to QSCPU?

P.S: As known it's possible to read/write from/to Q series PLC with MX Component. It's also available reading from QSCPU with MX component. But cannot write to safety cpu with MX component (written in Mx component manual).

Thanks.

Edited by Nizami_225

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I don't think you can write to the safety CPU.  I think it's locked because it's not supposed to be affected externally.  I know it is compatible with the E71 module as well as some CC-Link IE and MELSECNET modules.  Haven't had to touch one in years though, and never tried via MC protocol.

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As Crossbow says the whole point of the Safety CPU is that you cannot write to it from an external device. Everything regarding the safety CPU is more or less "locked down" for it's own protection... And you're basically referring to the whole point of operation yourself:

11 hours ago, Nizami_225 said:

P.S: As known it's possible to read/write from/to Q series PLC with MX Component. It's also available reading from QSCPU with MX component. But cannot write to safety cpu with MX component (written in Mx component manual).

 

Why would you even want to write to the safety CPU? The whole point of the safety CPU would be broken if you can write data directly into Bits/Words by external devices... You should use safety IO to handle incoming data.

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12 hours ago, kaare_t said:

Why would you even want to write to the safety CPU? The whole point of the safety CPU would be broken if you can write data directly into Bits/Words by external devices...

I have to write from PC in my situation. How would the whole point of safety cpu be broken? What do you mean exactly?

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Don't know how your system works, but I have been working with safety PLC's of another brand a lot.

That brand (German) has both failsafe and "normal" memory areas.

Values for the process like set points can remotely be written to the non-failsafe area, and inside the failsafe program be transferred to the failsafe memory area.

That PLC allows you to read a normal "grey" memory in the failsafe "yellow" program loop.

But you can't both read and write to a "grey" memory inside the "yellow" program loop.

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21 hours ago, Nizami_225 said:

 

On 7.6.2016 at 8:11 PM, kaare_t said:

Why would you even want to write to the safety CPU? The whole point of the safety CPU would be broken if you can write data directly into Bits/Words by external devices...

I have to write from PC in my situation. How would the whole point of safety cpu be broken? What do you mean exactly?

 

You can write a safety program/application that works perfect and that are affected/controlled by e.g. a computer. However what if you (or a different computer developer) does something wrong on the computer side... The whole application would break and possibly cause a safety issue. A safety controller should never be affected by anything else than "itself".

Do you trust a computer developer to not do a mistake on the computer side, taking control of your safety application?

And what if the computer breaks down (or a different non-safety PLC for that matter), it would also break the safety function. Essentially it's a chain of events leading up to the fact that you are using a safety CPU which should not be dependant on other possibly non-safety CPU's/computers.

So all in all: If you don't need the safety CPU, why did you use it in the first place? According to your chain of events you are good to go with a standard CPU...

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6 hours ago, kaare_t said:

So all in all: If you don't need the safety CPU, why did you use it in the first place?

 

As Bryll said

On 08.06.2016 at 11:43 AM, Bryll said:

Values for the process like set points can remotely be written to the non-failsafe area, and inside the failsafe program be transferred to the failsafe memory area.

I must to change some set points from my SCADA program when process is running. For example i want to change remotely value of pressure for start or stop of water pump i.e.

I mean I make program for my process and set "solid" values. Then I want to change some of them. What should I do?

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Use analog inputs to control your setpoint values...

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Why are you controlling the setpoints in the safety PLC?  That should be done in a normal PLC.

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