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TIMER & edge transition

Created by: Giuliano69 at: 1/21/2012 9:14 AM (5 Replies)

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1/21/2012 9:14 AM	Rate (0)
Giuliano69 Posts: 21 Rating: (0)	TIMER use to be enabled and started by positive bit transition. Is the positive edge used to enable or start a timer, required to happens from one scan cycle to another, or simply in the CPU just one instruction before the start/enable Timer call ? The documentation says (for example about FR) "When the RLO transitions from "0" to "1", FR <timer> clears the edge-detecting flag that is used for starting the addressed timer. A change in the RLO bit from 0 to 1 in front of an enable instruction (FR) enables a timer. " This definition could lead to believe that a simple CLR SET pair instructions would anyway start the timer. But it doesn't work. Is the start edge transition "masked" by the editor, linking a edge bit somewhere in memory, that is checked each scan cycle to that PARTICULAR variable/input declared before the timer, or is it simply related with the status bit of the CPU one instruction before? How exactly it works "under the hood" ?
Giuliano69 Posts: 21 Rating: (0)
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1/22/2012 6:58 PM	Rate (0)
Giuliano69 Posts: 21 Rating: (0)	I would kindly ask an HELP understanding why the TIMER do NOT be RESTART after the FIRST Time. Basically, in the attached example, I need a time delay each time a record is transfered to the HMI. The start signial is given by a memory variable in the FB, that I SET each time needed, and clear each time the Timer elapse. But it works only the first time. I tried to check with PLC Sim, but without success... The key networks in the attanchements are the follows : [code]TITLE = NTWRK 5 - Set Start input for timer to TRUE AN #ST_HMI_WAIT; = #ST_HMI_WAIT; NETWORK TITLE = NTWRK 6 - time load in pulse and start // set time to wait for hmi A #ST_HMI_WAIT; L S5T#20MS; SP "ST_HMI_Timer"; NETWORK[/code] Where am I wrong ? Any help will be appreciated :-) Attachment FB1.AWL.zip (31 Downloads)
Giuliano69 Posts: 21 Rating: (0)
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1/22/2012 8:02 PM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 6/8/2023 Posts: 6805 Rating: (1346)	Giuliano69 I would kindly ask an HELP understanding why the TIMER do NOT be RESTART after the FIRST Time. Basically, in the attached example, I need a time delay each time a record is transfered to the HMI. The start signial is given by a memory variable in the FB, that I SET each time needed, and clear each time the Timer elapse. But it works only the first time. I tried to check with PLC Sim, but without success... The key networks in the attanchements are the follows : TITLE = NTWRK 5 - Set Start input for timer to TRUE AN #ST_HMI_WAIT; = #ST_HMI_WAIT; NETWORK TITLE = NTWRK 6 - time load in pulse and start // set time to wait for hmi A #ST_HMI_WAIT; L S5T#20MS; SP "ST_HMI_Timer"; NETWORK Where am I wrong ? Any help will be appreciated :-) Dear Giuliano69, As I read the description I undestood that you activate a memory then wait until a period of time elapsed and then deactivate the memory and make it ready for the next time. Negative edge in M200.0 or (T0) can be used at an indication of elapsed time. [code] A M 200.0 //you activate this L S5T#10S SD T 0 // timer run --> wait 10s A M 200.0 //if memory and timer on at A T 0 //same time reset both R M 200.0 R T 0[/code] Sorry my English is not perfect and I just guessed what you mean.I hope my try be helpful as you requested in your P.M. Best regards, Hamid Hosseini
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1/23/2012 1:26 AM	Rate (0)
Giuliano69 Posts: 21 Rating: (0)	Thanks hdhosseini for your help. Three more question on the subject: I saw you swapped a pulse timer with a delay timer (SD vs SP); was this the problem ? I cannot see why the pulse couldn't work... you use a Merker memory bit, I used a BOOL Variable bit inside the FB instance DB. Is my solution still correct ? with reference of the subject: IF few lines after having reset the timer and the Signal (m200.0) in the SAME scan cycle we raise the signal, and then call the TIMER again, will the be edge transition of M200.0 be detected or it must happens in two DIFFERENT scan cycle ? For my test in PLCSIM it seems not to work, by I afraid it should be also by a program error....
Giuliano69 Posts: 21 Rating: (0)
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1/23/2012 2:23 AM	Rate (0)
Giuliano69 Posts: 21 Rating: (0)	I came back to the 3d because I cannot fix the problem even reversing the logic with SD -> SP. What may be is PARTICULAR (?) in may FB, si that the resetting of the BOOL start signial is processed many netwokrs before the starting of the TIMER,and the FB exit after having reset the bit. (The FB will be called later and a corespondent Jump will reach the starting of the TIMER) The setting of the BOOL starting signal is made networks , but it seems in the correct order Tring with PLCSim, it shows to work only the FIRST timer call. I can see the H_WAIT bool signial raising again, but the timer does NOT start again...... (sigh... ) Any idea what I am missing ? [code] A "H_WAIT" // HMI waiting ? JCN _000 // not waiting for HMI. poocess new data. Jump to ... A "ST_HMI_Timer" // if time is elapsed reset timer and flag R "H_WAIT" R "ST_HMI_Timer" BEU [/code] [code] AN "H_WAIT" = "H_WAIT" // set time to wait for hmi A "H_WAIT" L S5T#200MS SD "ST_HMI_Timer" BEU[/code]
Giuliano69 Posts: 21 Rating: (0)	Last edited by: Giuliano69 at: 1/23/2012 2:25 AM
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1/23/2012 1:55 PM	Rate (0)
Giuliano69 Posts: 21 Rating: (0)	Hi, I solved the problem and would like to share the solution Setting (prior to the TIMER call) and resetting the staring variable in DIFFERENT places, si the problem. The timer is told to keep trace of the edge transition of the enabling variable. The edge transition is NOT evaluated as other Memory bit, but the timer HAS to be recalled at least once with the staring variable in the false value. I do not know how exactly the timer is done inside, but the enable variable is not linked to the timer with a "classic" edge bit. Perhaps it is a macro-code, that is expanded with an internal variable memorizing the input enabling value....
Giuliano69 Posts: 21 Rating: (0)
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