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SCL - bit commands

Created by: 0_Einstein at: 1/30/2012 5:36 PM (26 Replies)

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1/30/2012 5:36 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 3/20/2025 Posts: 15736 Rating: (2488)	Ok, I have searched for SCL commands that replace the various LADder logic functions. The on/off are easy: true/false. SET RESET Rising Edge -\|p\|- Falling Edge -\|n\|- How do the boolean pieces coexist in SCL versus ladder? Let's say I have a reset / set latch configured in Ladder and want to convert that to SCL. If I set a value to TRUE in SCL, is that in fact acting as a latch SET? Likewise for FALSE being latch RESET? The documentation is lacking for the boolean stuff, or if it is there, you have to know the answer in order to find it.
	science guy
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1/30/2012 7:24 PM	Rate (0)
Gabriel de Oliveira Bronze Member Joined: 2/16/2011 Last visit: 1/13/2025 Posts: 229 Rating: (28)	Hello, See this.. UMENCHO Hello, There ishttp://support.automation.siemens.com/WW/view/en/36932465. The new SP2 manual has a whole section dedicated to SCL. You can find it http://support.automation.siemens.com/WW/view/en/57199536 Just to start with... Best regards, Hristo Mihalev Good Lock
	Gabriel de Oliveira It Works? Rate It.
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1/30/2012 9:00 PM	Rate (1)
Denilson Pegaia Platinum Expert Joined: 9/23/2005 Last visit: 3/14/2025 Posts: 4406 Rating: (1475)	Hi, as example, a RS flip flop: if S=True then Q:=true; end if; if R=true then Q:=true; end if;
	Denilson Pegaia Siemens Industry Sector Technical Support
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This contribution was helpful to 1 thankful Users Tomy Master

1/30/2012 9:33 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 3/20/2025 Posts: 15736 Rating: (2488)	Thanks Gabriel de Oliveira Unfortunately, the various set/reset, rising/falling edge detection functions are unavailable for SCL. It states, "For SCL: You must write code to replicate this function within your application.", for each of the items. It also does not describe how bits are turned on/off. In ladder logic, if I include a -( )- and do not have 'power flow' to the coil bit, it turns off that bit. In SCL, if I skip over logic that would ordinarily set a value, yet have no logic that resets the value, what state will it have at the end of the SCL function? This is quite unsettling as I have many string-handling functions that work so much better in SCL, yet, they often require edge triggering to activate pieces of logic, then SET or RESET status bits based on the results. I'm trying to convert some old ladder logic to SCL to take advantage of these capabilities. Anyone have sample code to replicate set/reset, rising/trailing edge detection, and can describe what happens as described above?
	science guy
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1/31/2012 10:49 AM	Rate (1)
Denilson Pegaia Platinum Expert Joined: 9/23/2005 Last visit: 3/14/2025 Posts: 4406 Rating: (1475)	Hi, here is a example of edge detection: myoutput := (myinput=true) and (lastmyinput= false); mylastinput := myinput;
	Denilson Pegaia Siemens Industry Sector Technical Support
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1/31/2012 11:37 AM	Rate (0)
Gabriel de Oliveira Bronze Member Joined: 2/16/2011 Last visit: 1/13/2025 Posts: 229 Rating: (28)	Hello; I created a sample project with some basics comands... see../tf/WW/en/Posts/68786#338764 Regards
	Last edited by: Gabriel de Oliveira at: 1/31/2012 6:09 PM Gabriel de Oliveira It Works? Rate It.
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1/31/2012 3:04 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 3/20/2025 Posts: 15736 Rating: (2488)	These responses are really useful but do not answer my questions, or maybe they do but do not include explanation. Ladder logic : -(S)- & -(R)- are very useful in that you can put your ladder logic in "logical" groupings, like all the initialize, manual mode, auto mode, setup mode (calibrations), fault handling, etc. together. For each condition that needs to turn on a bit, just use the 'set' for that mode. For each condition, like first-scan, fault acknowledge, step completion, etc., a 'reset' to turn it back off. From what I'm reading about the feedback on SCL, it treats all bits as -(S)- and -(R)- in that if the logic is not actively affecting a bit, the bit remains unchanged. Ladder logic : -( )- gets turned off if the logic isn't actively turning it on. To do this in SCL, just make sure the bit is run every scan without any surrounding structures like FOR/IF/CASE/etc. and it always activates the logic for that bit and its on/off as needed. It would be nice if rung-by-rung we could set whether it's SCL or ladder so we could get the best of both. I know other PLC makers allow this and it's very useful. For me, it would make it EASY to understand these oddities and not care why there are no set/reset, and N_TRIG/P_TRIG commands built into SCL. Guess I'll figure it out eventually.
	science guy
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1/31/2012 4:22 PM	Rate (0)
Gabriel de Oliveira Bronze Member Joined: 2/16/2011 Last visit: 1/13/2025 Posts: 229 Rating: (28)	Dear huggy_d1, Each language has its purporse. Example: Set, reset flags, logical combination, etc (FBD or LAD) Automatic cycle, sequence (GRAPH) Math, conversions, Expressions, PID (SCL) You can do anything in any Language, but it's not usual. Regards
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1/31/2012 4:34 PM	Rate (1)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 3/20/2025 Posts: 15736 Rating: (2488)	Gabriel de Oliveira Dear huggy_d1, Each language has its purporse. Example: Set, reset flags, logical combination, etc (FBD or LAD) Automatic cycle, sequence (GRAPH) Math, conversions, Expressions, PID (SCL) You can do anything in any Language, but it's not usual. Regards Understood long before I posted to the thread. Your last sentence is the key to the thread. I want to do "anything" with the SCL, but the documentation is lacking on how it treats bits in relation to ladder logic. If I could put ladder and SCL together in the same routine, that would solve the problem as I would use the bit logic in LAD and the math/conversion/expression/string handling in SCL and it would all peacefully coexist. It seems nobody knows the answer to my questions. I'll let it go.
	science guy
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1/31/2012 4:52 PM	Rate (0)
Gabriel de Oliveira Bronze Member Joined: 2/16/2011 Last visit: 1/13/2025 Posts: 229 Rating: (28)	Hello, You can do anything in SCL, LAD logic will loocks like.. M0.0 Q0.0 \|-\| \|----------------------------( )--\| IF M0.0 THEN // Statement section IF Q0.0:=TRUE; ELSE // Statement section ELSE Q0.0:=FALSE; END_IF; Regards
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