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How can I check in s7-300 PLC if Real-time clock was changing by PG?

Created by: dzeezz at: 7/24/2007 9:35 PM (3 Replies)

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7/24/2007 9:35 PM	Rate (0)
dzeezz Bronze Member Joined: 10/23/2006 Last visit: 5/22/2023 Posts: 48 Rating: (1)	Hello I need to know how can I check if someone change real time clock using programator. I wrote a program in every going PLC into RUN mode I calculate new time and date of start OB10 ( I use SFC28). My program works fine, but thre is one problem: If someone change SYSTEM Date and Time (for example 10 days in the past) I can't discover it in my program so there is stil old DATE and TIME and in my example it must 10 days elapsed to start OB10. Thanks for help.

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7/24/2007 11:08 PM	Rate (0)
Mojo Bronze Member Joined: 3/27/2006 Last visit: 5/16/2023 Posts: 90 Rating: (13)	At startupread the clock with SFC1 "READ_CLK" and store the value. You would expect the clock to go forward. Periodically read the clock and compare to the stored values. If the stored value is not in the past then someone turned the clock back.
	"I never let a cowboy make the coffee." Yeah, thats what Granny always said to my Grandad. And he'd say: "Never tell a joke that ain't that funny more than once." "And if you wanna hear God laugh, tell Him your plans." Van Zant "Help Somebody"
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This contribution was helpful to 1 thankful Users john2pink

7/25/2007 10:22 AM	Rate (0)
dzeezz Bronze Member Joined: 10/23/2006 Last visit: 5/22/2023 Posts: 48 Rating: (1)	Thank you. I thought about that solutions, but I hope that there are some way to use system bits. Have a nice day

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7/25/2007 2:46 PM	Rate (0)
Mojo Bronze Member Joined: 3/27/2006 Last visit: 5/16/2023 Posts: 90 Rating: (13)	You are right, a system bit would be a much cleaner and more precise way to do it. Does anyone know if there is one?
	"I never let a cowboy make the coffee." Yeah, thats what Granny always said to my Grandad. And he'd say: "Never tell a joke that ain't that funny more than once." "And if you wanna hear God laugh, tell Him your plans." Van Zant "Help Somebody"
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