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| 12/2/2010 11:56 PM | |
Joined: 10/7/2005 Last visit: 9/13/2024 Posts: 3020 Rating:
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Hello misak_s there's a couple of other ways I can think of: 1.) Add a CP342-5 Profibus DP Master card to your rack. It's Profibus I/O's do NOT count towards the CPU's I/O range (they are handled entirely inside the CP342-5 and all of its "Profibus I/O's" appear only as DB values as far as the CPU is concerned). Should you choose to go down this path, start by having a look at the two links below: What are the differences between an integrated DP interface of my CPU (e.g. CPU 315-2 DP) and the DP interface of the CP 342-5? What should you watch out for when configuring a CP342-5 as DP master? 2.) Keep the PAC's on the CPU's D port and use a smaller I/O type as you suggested. Then read out all sorts of additional values withso called "acyclic Data record acccess" via usageof SFB52/53 (or SFC48/49). This will require some additional programming effort though, moreso since you will need to multiplex the SFB52/53 (or SFC48/49) calls as 4 is the maximum of simultaneous calls that you can have in a 312 (see HERE for more on this). Note too the following differences betwen cyclic and acyclic access: Cyclic: ALL I/O's of ALL DP Slaves are updated EVERY Profibus scan. Acyclic: OnlyONE DP Slaves can supply data per Profibus scan (only one acyclic message is allowed per Profibus scan, since you request data with an acyclic message, you need at least two Profibus scans before you get the requested data) As such, you typically use acyclic dataonly for non time critical and non control related aquisition of values. Should you choose to go down this path, start by having alookat chapter 5.3 of the SENTRON PAC PROFIBUS DP Expansion Module manual which contains the info about available Data records that you can access this way. Having said all the above, the easiest choice is possibel to simply go a CPU with bigger I/O range as Dariusalready suggested but I hope this helps anyhow. |
Last edited by: fritz at: 12/3/2010 2:39 AMLast edited by: fritz at: 12/3/2010 12:00 AMCheers |
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