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CPU clock stops when power is off

Created by: Pontus at: 1/28/2008 12:50 PM (6 Replies)

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1/28/2008 12:50 PM	Rate (0)
Pontus Posts: 51 Rating: (1)	Hello I have a S7 312 CPU, together with a small touchpanel. I dont know how to monitor the CPU clock in Step 7, so I do that by showing the tag on the OP. First I wanted to let the OP controll the time, but that wasnt possible because the clock stops when the power is off. So now I let the CPU to be the master of the clock. I have copied this project: http://support.automation.siemens.com/WW/view/en/26961517 so I canhave the summer/winter switch automatic. But the problem is that every time I turn the power off, the CPU clock stops! If I just set the CPU in stop mode, I can see on the OP that the time is stopping, and when I put it in run again the clock is corrected to where it sould be (everything OK). But if the power dissapear, the clock stops and begins again where it last stopped. Why is that? I removed all the program in the CPU and just saved the "Read clock", but the time still stops. I still have the same program on the OP, if that could affect something. The reason for that is that I dont know how to monitor the clock in Step 7...
Pontus Posts: 51 Rating: (1)
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1/28/2008 4:30 PM	Rate (0)
Aret Posts: 2348 Rating: (264)	Do you connect date/time to internal tag? What output field do you use?
Aret Posts: 2348 Rating: (264)
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1/29/2008 8:30 AM	Rate (0)
Pontus Posts: 51 Rating: (1)	Aret Do you connect date/time to internal tag? What outputfield do you use? Sorry, but could you bescribe more in detail what you mean? I have now disconnected the OP so it could not affect the time, but it still stops. I use theREAD_CLK in step 7. but then I cant monitor it so I use the function DT_TOD (extracts time from date and time) ant there you could se that the clock stops counting while its off. The time is saved in datablocks.., on the output of Read clock. As it is now, I have no program now, all I have is OB1 calling for an FC that have the function READ_CLK, and the output is shown in DB1 with the adress DATE_AND_TIME.
Pontus Posts: 51 Rating: (1)
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1/29/2008 10:55 AM	Rate (0)
Pontus Posts: 51 Rating: (1)	I have nowtested the exact same program on a 315-2DP and the clock works fine. And when I download the same program back to my 312, the clock is stopping. Have I missed something here? Because the clock on 312 should not stop, right? Is there any settings on the CPU, or maby something wrong with it?
Pontus Posts: 51 Rating: (1)
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1/29/2008 11:55 AM

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Zenta

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Pontus
I have nowtested the exact same program on a 315-2DP and the clock works fine. And when I download the same program back to my 312, the clock is stopping. Have I missed something here? Because the clock on 312 should not stop, right? Is there any settings on the CPU, or maby something wrong with it?

Hi Pontus,

I chek for you in the CA 01

312 time:

Time
Clock
Software clock	Yes
buffered and synchronizable	No
Deviation per day, max.	15s

315 time:

Time
Clock
Hardware clock (real-time clock)	Yes
buffered and synchronizable	Yes
Deviation per day, max.	10s

I think this is the solution. Sorry

Best regards Zenta

1/13/2009 12:18 PM	Rate (0)
MIRO1 Posts: 1 Rating: (0)	Hello, i have the same problem on a CPU313, this one has also a software clock, a 313C has a hardware clock.... so if i had understand correctly there is no solution for this problem? thnx
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