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Using WRIT_DBL

Created by: salrandazzo at: 5/11/2015 2:20 PM (5 Replies)

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5/11/2015 2:20 PM	Rate (0)
salrandazzo Posts: 57 Rating: (8)	My need is to use WRIT_DBL and READ_DBL to store and retrieve data to/from flash memoy card. My purpose is to work as follows: about writing When new data are available, I write them in DB5, in working memory Then I rise the write_req_flag When the write_req_flag is high, the write operation (FC2) takes place, writing data from DB5 (work memory) into DB2 (Load memory) When the write operation is over (busy flag low) I reset the write_req_flag. about reading: when the program starts (OB100) I rise the read_req_flag when the read_req_flag is high, the read operation (FC3) takes place, reading data from DB2 (Load memory) into DB5 (work memory). DB2 attribute is "Only store in load memory". The attribute "Optimized block access" is not set. DB5 attribute "Optimized block access" is not set. When I try to compile my program (see attachment) I get an error on WRIT_DBL block. The error is: "Network 1,The reference information is inconsistent. The block cannot be compiled." No errors on the READ_DBL operation. Any hint? Attachment rw_dbl_test.zip (524 Downloads)
salrandazzo Posts: 57 Rating: (8)	Last edited by: salrandazzo at: 5/11/2015 2:23:32 PM
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5/11/2015 3:55 PM	Rate (0)
William_B Posts: 5225 Rating: (1165)	Hi. Please see the HINTS in the attachment: x3 pictures and modified program. The software is giving us a problem with the data consistency.. so we "force" the software to recognise the consistency. Greetings. w Attachment Design Idea_Write to memory DB.zip (779 Downloads)
William_B Posts: 5225 Rating: (1165)
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This contribution was helpful to 1 thankful Users salrandazzo

5/11/2015 3:59 PM	Rate (0)
salrandazzo Posts: 57 Rating: (8)	Seems to be a TIA portal problem. I deleted the first project and I made it brand new, from the scratch. Now the compilation error on the WRIT_DBL block seems to be disappeared.
salrandazzo Posts: 57 Rating: (8)
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5/11/2015 4:22 PM	Rate (0)
salrandazzo Posts: 57 Rating: (8)	William_B Hi. Please see the HINTS in the attachment: x3 pictures and modified program. The software is giving us a problem with the data consistency.. so we "force" the software to recognise the consistency. Greetings. w Thank you William, I'll try to use your method. So far I think that I solved the problem by re-writing the project from the scratch. When the test program will be up and running I'll upload it.
salrandazzo Posts: 57 Rating: (8)	Last edited by: salrandazzo at: 5/11/2015 5:12:24 PM
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This contribution was helpful to 1 thankful Users William_B

5/12/2015 3:59 PM	Rate (1)
salrandazzo Posts: 57 Rating: (8)	I wrote a working version of the WRIT_DBL and READ_DBL. Here the description: This program demonstrates the use of the WRIT_DBL and READ_DBL instructions. The purpose is to store information on the flash memory. This is the data organisation: DB1 (load flash memory) is used as retentive memory. DB2 (work memory) is used for normal work. DB1 is updated when DB2 changes with a WRIT_DBL operation that copies DB2 to DB1. DB1 is read into DB2 with a READ_DBL only at startup (OB100). When a request (write_record_request) arises, a new record will be written in the work memory (DB2) The work memory will then be written by FC1 into the load (flash) memory using WRIT_DBL. We just write the time (DTL 12 bytes) when the request goes on. A write pointer counts the next record to be written (0 to 5). When you turn off the power supply, data won't be lost and will be read at power on (OP100). The advantage if this method is that we have a lot of space to use, much more than the normal retentive memory. We can use part of the 4MB CPU load memory (it will also accomodate program and working DB) and a possible external 2 / 12 / 24 MB SMC card . Attachment READ_WRITE_DBL.zip (872 Downloads)
salrandazzo Posts: 57 Rating: (8)
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5/13/2015 7:34 AM	Rate (0)
William_B Posts: 5225 Rating: (1165)	Hi. Thank you for sharing this information. A few notes.. As far as I know there is (was?) some issues with the standard instructions used for data log recording.. something to do with not using the full capacity of the card. If that problem is still there - your example program will be good to build on to use the full memory capacity of the MMC card. Do know that the firmware V4.0 (and higher) now have instructions to use the MMC as memory for recipes. (The S7-200 had this too.) Where someone does not have FW4 - this code will be most welcome. I do not know if the read / write cycle becomes longer as the access path becomes "longer". This has the potential of badly effecting PLC cycle.... That is the only reason I can think of that there is a limits to the data log recoding with the standard instructions. (maybe) I would encourage you to re-publish your sample program on this forum as a "TIP". More people will see your good work. If you have the time it would be nice to give some tips-and-tricks ideas that will help the others in the future. Keep up the good work! w
William_B Posts: 5225 Rating: (1165)
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