7/17/2013 8:53 PM |
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Posts: 621 Rating: (10) |
good topic ICE timers |
7/22/2013 3:56 PM | |
Joined: 10/7/2005 Last visit: 9/22/2024 Posts: 3021 Rating: (1054)
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Dear all here's my take on things: First thing first, S5 Timers BCD format and "wastage" of bit 14&15 date back to the way a Time value was declared in an S5. Back thenyou had to explicitly declare the time base which was either 0 (10ms) 1(100ms) 2(1s) 3(10s) A 1 second Timer could as suchhad Setpoint of either: 001.2 (1*1s, accuracy of 1s) 010.1 (10*100ms, accuracy of 100ms) 100.0(100*10ms, accuracy of 10ms) Note how a dot seperated the (BCD) time value and the time base. The time base was as such simply taken over as the bipattern for thebit12&13, wheras the BCD time value used bits 0-11. Stating things like "S5Time datatype is 94% wastage of memory" is pretty meaningless in my opinion and their (16 bit) Setpoint is still 50% more efficient than an (32 bit) IEC Timersetpoint (let alone the already mentioend IDB storage that is consumed by an IEC Timer). As for other things to note about S5 Timers versusIEC Timers that I thinkhaven't been mentioned yetin this thread: 1.) Update: S5 Timers are updated by the operating system asynchronously to the user program scan. IEC are updated when called by the user program. Sounds trivial but can lead to unintended consequences when using S5 Timers and for example directly questioning the Timer (e.g. A T 7) in more than one place in the user program. The solution to this is to alwasy assign a bit to the output of the S5 Timer where it is started and then questionthat bit elsewhere in the user program. 2.) FC/FB Parameter usage: S5 Timers can be passed on to FC's and FB's, IEC Timers can not. 3.) Accuracy: S5 Timersaccuracy is based on its timebase. IEC Timers accuracy isconsistent across the whole setpoint range. Starting an S5 Timer for example with a setpoint of 10s meansit willbe counteddown by the OSin 100ms steps andas such have an accuracy of 100ms (i.e. it can expire anytimebetween 9.9s and10s). Starting an S5 Timer howeverwitha setpoint of 9.99s meansit will be counted down in 10ms steps and have an accuracy of 10ms (i.e. it can expire anytime between 9.98s and 9.99s). To make matters worse, in an S5 you had to specify the timebase (see above) and were as such aware of the timebase and accuracy (and would of course always nominate 1sec. as KT 100.0 instead of KT 001.2). The more user friendly S7 way of specifying the time for an S5 Timer now hides the timebase from use (and as such the accuracy). 4.) Software redundancy: IEC timers are supported as part of the redundantprogram, S5 Timers are not That's all I can think of for now on this subject and I hope it helps |
Last edited by: fritz at: 7/23/2013 2:03 AMFixed up expire time ranges Cheers |
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This contribution was helpful to6 thankful Users |
7/22/2013 4:40 PM | |
Posts: 378 Rating: (73) |
Hello fritz, Thanks for detailed explanation, 94% wastage of memory is in respect to the capacity of 16bit memory not in respect to IEC timers. Regards, |
7/23/2013 3:08 AM | |
Joined: 10/7/2005 Last visit: 9/22/2024 Posts: 3021 Rating: (1054)
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Hello Juergen all is well Down Under (or wherever else I've been in the past few weeks) and I hope you enjoy the summer weather in good old Germany. As for "S5 Timers can be passed on to FC's and FB's, IEC Timers can not": FC's/FB's have the parameter data type "TIMER" aswell as "S5TIME" which allows you to pass onthe S5Timer number and the S5Time setpoint respectively. For IEC timers you can only pass on the Time setpoint (parameter data type "TIME" which you correctly noted). As IEC Timers have no number (their IDB is their "number"), there is no "IEC timer number" parameter. You could though specify "BLOCK_DB" as an input and use it to pass on the IEC timers IDB to the FC/FB (which you wouldn't in case of an FB where you'd of course you the IEC timer as a multi instance call). I suppose this difference is probably more of a semantic nature than a anything else, but still a difference. Last but not least, one other difference between S5Timers and IEC Timers is that the S5 Timer outputs the remanining time (time counts down to zero) whereasan IEC Timer outputs the elapsed time (time counts up to the setpoint). |
Cheers |
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This contribution was helpful to3 thankful Users |
7/23/2013 7:49 PM | |
Posts: 8946 Rating: (999) |
Fully agree. |
7/29/2013 10:12 AM | |
Joined: 4/24/2009 Last visit: 8/20/2024 Posts: 2682 Rating: (135) |
New question splitted to “hanging” outputs on IEC Timers? Best regards O_Moderator |
2/4/2014 11:55 AM | |
Joined: 8/27/2010 Last visit: 4/13/2024 Posts: 417 Rating: (37) |
Hi! I prefer to use clock memory and cyclic interrupt OB's
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