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How to read/ write data from 18 different S7-1200 CPUs using one master S7 -1200 CPU

Created by: sunil santhosh at: 10/11/2014 7:16 AM (6 Replies)

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10/11/2014 7:16 AM	Rate (0)
sunil santhosh Member Joined: 8/10/2013 Last visit: 4/25/2024 Posts: 3 Rating: (0)	Dear All, Could please suggest a method to read few datas ( from Data block ) from 18 diffrennt s7 -1200 CPus with a common S7 -1200 CPU .

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10/13/2014 7:00 AM	Rate (0)
Kashir Bronze Member Joined: 10/24/2012 Last visit: 2/28/2025 Posts: 310 Rating: (21)	Dear AutoGen, According to my knowldge you can only share data between 8 CPUs CPU to CPU communication and in 1215 and 1217 you can share data with 12 CPUs.
	Kashir Saeed. If this information helps you,then you can use the rate function.
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10/13/2014 3:36 PM	Rate (1)
0_Einstein Diamond Member Joined: 7/7/2010 Last visit: 3/10/2025 Posts: 15721 Rating: (2487)	AutoGen_541556 Dear All, Could please suggest a method to read few datas ( from Data block ) from 18 diffrennt s7 -1200 CPus with a common S7 -1200 CPU . If you poll each device manually using a triggered GET instruction, you can control how many S7 connections are established at one time. Each HMI takes 1 connection, and the first HMI takes and extra connection (total of 2 connections on first HMI). That leaves 6 or 10 depending on PLC. An online connection to program, monitor or download will require a connection, so be sure and leave one open! You can quickly see how this could get out of control very quickly if not properly managed. Depending on how fast your PLC scan time is, and how often you need to read the 18 PLCs, you should be able to GET the DB from each PLC one, two, or three at a time without too much of an impact to the overall scan time. Just increase the communications load % from the default of 20% to say 30% or maybe 40% max. Look at the GET trigger input and monitor the Done/Busy/Error bits to reset each trigger. Since there are so many, it is possible some may be offline at some point, so allowances must be made to allow for that. If you need simultaneous updating, you need s7-1500, or a cascading structure. For 18, that may be: master \| \ PLC PLC \| \ \ \ PLC PLC PLC PLC .... until you can capture and feed upstream all data. This structure however fails miserably if any plc goes down that also polls downstream, and is further a problem the higher up it is in the tree. If your process can tolerate this, that's fine, but you need to think about it.
	science guy
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This contribution was helpful to 1 thankful Users Kashir

10/13/2014 8:00 PM	Rate (0)
sunil santhosh Member Joined: 8/10/2013 Last visit: 4/25/2024 Posts: 3 Rating: (0)	Thanks ... For your suggestion . It is not nessary that communication should be simultaneous. can I go for modbus TCP/IP . Option so that master can poll each salve Plc one by one.?

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10/13/2014 8:09 PM	Rate (0)
0_Einstein Diamond Member Joined: 7/7/2010 Last visit: 3/10/2025 Posts: 15721 Rating: (2487)	sunil santhosh Thanks ... For your suggestion . It is not nessary that communication should be simultaneous. can I go for modbus TCP/IP . Option so that master can poll each salve Plc one by one.? You could, but it is much easier to use the GET block between Siemens PLCs. It is very simple, and you get the DB contents from the remote PLC into a local DB automatically with the same structure. You do not need to do anything to fit data into the register concept and no conversions are necessary as a result. The first time I used GET and was very pleased at how easy it went. The trigger for the MB/TCP communications is very similar to the trigger for GET. Siemens sets up the comm instructions so the control structure for handling done/busy/error and status is virtually identical.
	science guy
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10/14/2014 7:33 PM	Rate (0)
sunil santhosh Member Joined: 8/10/2013 Last visit: 4/25/2024 Posts: 3 Rating: (0)	Thanks for your valuable infromation . I never used this function. Now that project is it's submittals stage . I am going a head. Could you please send me link to some sample program?

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10/14/2014 7:37 PM	Rate (0)
0_Einstein Diamond Member Joined: 7/7/2010 Last visit: 3/10/2025 Posts: 15721 Rating: (2487)	sunil santhosh Thanks for your valuable infromation . I never used this function. Now that project is it's submittals stage . I am going a head. Could you please send me link to some sample program? Quick search on these forums by typing "get put s7-1200" in the search box up there ^^^^^ gave me this as the top result: /tf/WW/en/Posts/68281
	science guy
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