Skip to Content

Register Login

Industry Online Support

Technical Forum

Navigation

Scan time

Created by: salah21250 at: 5/31/2011 2:10 PM (10 Replies)

Rating (3)

Thanks 3

Result pages:: |; 1 | 2; |

11 Entries

Entries per page: 10 | all

5/31/2011 2:10 PM	Rate (0)
salah21250 Posts: 18 Rating: (0)	hello; I have projetc with PCS7 V6.2 SP2, I calculate the scan time of every OB wich is used in this project. i want to kwon if thereis a manner to calculate globlal scan time of the all project. thanks in advance
salah21250 Posts: 18 Rating: (0)
Suggestion To thank Quote Answer

5/31/2011 2:48 PM	Rate (1)
Silent Bob Posts: 836 Rating: (100)	Hi, there is a FAQ accoring this topic. It helps you to calulate the scan time of all watchdog OBs. http://support.automation.siemens.com/WW/view/de/19688569 At least you have to consider the cycle time of you cyclic block (OB1) and the cylce time of your failure OBs (if relevant). In newer PCS 7 versions you could use the block CPU_RT. But its not part of your PCS 7 version.
Silent Bob Posts: 836 Rating: (100)
Suggestion To thank Quote Answer

6/2/2011 3:25 PM	Rate (0)
fanlfc Posts: 13 Rating: (1)	OB1 has the lowest priority for execution amongst the all OB's, so i guess the the scan cycle time of the complete system should be the execution time of OB1
fanlfc Posts: 13 Rating: (1)
Suggestion To thank Quote Answer

6/2/2011 3:33 PM	Rate (0)
minhajie Posts: 96 Rating: (10)	Hi salah21250, The link given above is to do with the OB interrupt tie scan. There is actually no such thing as the overall project scan cycle. You can refer this to the CPU scan cycle if you want which will the best answer to your question. This you can find if you go online in the hardware configuration and check the online CPU status. Hope this was helpful. regards, mk
minhajie Posts: 96 Rating: (10)
Suggestion To thank Quote Answer

6/3/2011 10:17 AM	Rate (0)
Yoga Shankar Posts: 288 Rating: (22)	hello, there is one thing to be noticed, OB1 has the least priority of execution. hence the average scan time of OB1 is the scan time of the overall project, since any and all OB's will interrupt OB1 and OB1 will be the first to start and the last to end.
Yoga Shankar Posts: 288 Rating: (22)
Suggestion To thank Quote Answer

6/4/2011 12:02 PM	Rate (0)
Jazz_M Gold Member Joined: 9/6/2008 Last visit: 5/7/2022 Posts: 1121 Rating: (86)	Hi well there is nothing called as over all scan cycle, But overall scan cycle depends on the programmer, By default the program is called in OB35, you can set the OB that are required by you. You have to segregate you project as critical and non critical inputs/outputs, based on that you can call your program in diffrent Cyclic OB's Have fun...
	Jazz
Suggestion To thank Quote Answer

6/5/2011 7:40 PM	Rate (0)
Yoga Shankar Posts: 288 Rating: (22)	Tagolover Hi well there is nothing called as over all scan cycle, But overall scan cycle depends on the programmer, By default the program is called in OB35, you can set the OB that are required by you. You have to segregate you project as critical and non critical inputs/outputs, based on that you can call your program in diffrent Cyclic OB's Have fun... What is to be understood about OB 30 to OB 38 is that the interval of calling these OB's is fixed, but it does not make any adjustment based on the time taken to complete one scan of the code in the OB. So if the time required to scan thru or execute the code written in OB 35 were to exceed 100 ms, the CPU would go into stop due to watch dog error. Care has to be taken to limit the length of code or in PCS7 parlance, the number of control blocks called in charts assigned to OB35 run time group. the other way around this is to modify the interrupt cycle of OB 35 to match the code execution time. even this can be estimated. each runtime group has one FC designated for it self and this is called in OB1. so you could use the time start and end blocks to measure this length of time. of course, we need not go into this level of byte code level debugging. If the charts are optimised for run time ( using the option available in the CFC editor) the potential problems will be foreseen and the user will be warned.
Yoga Shankar Posts: 288 Rating: (22)
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users Jazz_M

6/8/2011 10:29 AM	Rate (0)
Krrish !! Posts: 73 Rating: (6)	salah21250 hello; I have projetc with PCS7 V6.2 SP2, I calculate the scan time of every OB wich is used in this project. i want to kwon if thereis a manner to calculate globlal scan time of the all project. thanks in advance dear salah21250, If what you are looking for is overall system time, then the scan-cycle time entry in diagnostic buffer would suffice. What is important to understand is that in order to calculate overall cycle time, beside the cyclic OBs scan-type for restart OBs, event-triggered and interrupt OBs also must be considered. Regards, Krrish !!
Krrish !! Posts: 73 Rating: (6)
Suggestion To thank Quote Answer

6/8/2011 10:38 AM	Rate (0)
Krrish !! Posts: 73 Rating: (6)	Dear salah21205, Please check the attachment. Hope this is what you are looking for. Regards, Krrish!! Attachment OBinfo.zip (477 Downloads)
Krrish !! Posts: 73 Rating: (6)
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users dchartier

10/3/2012 4:55 PM	Rate (0)
DLittlejohn412 Posts: 55 Rating: (1)	Krrish !! Dear salah21205, Please check the attachment. Hope this is what you are looking for. Regards, Krrish!! Hello what is the attachment? S7 does not recognize it as a project? How do I open this to see what it is?
DLittlejohn412 Posts: 55 Rating: (1)
Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Follow us on