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S7-1200 - Indirect Addressing of data within a DB

Created by: Naaltje at: 3/27/2014 12:40 PM (12 Replies)

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3/28/2014 1:16 PM	Rate (0)
0_Einstein Grandmaster-Expert Joined: 7/7/2010 Last visit: 12/29/2025 Posts: 16332 Rating: (2520)	I searched for "s7-1200 peek scl" in the search box ---^^^^ up there////// and came up with this helpful link: /tf/WW/en/Posts/69529
	science guy
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3/31/2014 12:54 PM	Rate (0)
ramiv Posts: 55 Rating: (1)	Hi about the PEEK, i suspect that if you use optimized DB-s it is impossible to use PEEK as you do not know where the data resides in the datablock. Should try this when i have some spare time. Ie you do not see the byte-adresses any more if you choose optimized access for particular datablock. This possibility to access arrays with index from another variable directly is one of the few things that i really like in TIA-sw. Also you can add items into (optimized) DB-s without having to modify existing code because the byteadresses have changed when you added some bit on the middle of the DB.
ramiv Posts: 55 Rating: (1)
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3/31/2014 4:25 PM	Rate (0)
0_Einstein Grandmaster-Expert Joined: 7/7/2010 Last visit: 12/29/2025 Posts: 16332 Rating: (2520)	ramiv Hi about the PEEK, i suspect that if you use optimized DB-s it is impossible to use PEEK as you do not know where the data resides in the datablock. Should try this when i have some spare time. Ie you do not see the byte-adresses any more if you choose optimized access for particular datablock. This possibility to access arrays with index from another variable directly is one of the few things that i really like in TIA-sw. Also you can add items into (optimized) DB-s without having to modify existing code because the byteadresses have changed when you added some bit on the middle of the DB. Yes, peek is not useful or even possible with optimized DBs. With Optimized DBs you can use custom datatypes to make it easy to look into the data. You can also pass large chunks of a custom datatype into an FB, use the AT overlay and read bytes from the custom datatype. Many ways to access the bits/bytes. In S7-1200, you can read bits/bytes using the slice, but it does not work with indirect addressing as far as I know. To access byte # 10, myTag.b10 To access bit # 10, myTag.x10 To access word # 10, myTag,w10 To access word # n, it would be nice if it was myTag.w[n] but that does not work. If you pass myTag into an FB, you can then via the AT overlay, access all the bytes indirectly. Post your results.
	science guy
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