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1/27/2010 7:35 AM | |
Joined: 3/18/2009 Last visit: 2/8/2022 Posts: 306 Rating: (94) |
I don't know if the concept of memory retentivity in S7 300 CPU is known to you. I quote below certain relevant part fromthis manual. (chapter 4)
Now since you can adjust the number of timers and counters that would be retentive (with a maximum limit of course) this was referred to as "Adjustable Retentivity" earlier. (And is still done in VIPA CPUs). It is now, however, referred to as retentivity which is configurable in S7-300 specifications. |
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1/27/2010 8:03 PM | |
Posts: 14 Rating: (0) |
Thanks for your replies and what about the third question |
1/27/2010 8:41 PM | |
Joined: 9/27/2006 Last visit: 4/27/2024 Posts: 12257 Rating: (2665)
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Hello has100; The DRUM instruction is available in the TI-S7 conversion library of Step 7, so the best place for you to look for the original function would be in the programming manuals for the TI 505; look here, in chapter 6 (RLL instructions; 6.17: Time-driven DRUM; 6.19: Time/Event driven DRUM): http://support.automation.siemens.com/US/view/en/17519025 Think of a DRUM instruction as the equivalent to an electromechanical stepper switch, rather like a player-piano sheet or the mechanism of a music box. It consists of a series of 16 steps that each control 16 output coils at once, so every step manipulates a different operating stage of a process. It is an early version of a Grafcet sequencer(see S7-Graph). You can "step through" the different steps in order, either with event-based or time-based transitions. Drums were used to control a singlr machine or process in a hardwired sequence of states. I have seen them used in a bottle forming plant, where the output coils controlled the different motions of the glass molding machines.Today, modern sequencers are usually programmed usingtechniques such as Grafcet. Hope this helps, Daniel Chartier |
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