Skip to Content

Register Login

Industry Online Support

Technical Forum

Navigation

Save Date and Time into an array in a DB

Created by: Tech74 at: 12/5/2014 11:16 AM (3 Replies)

Rating (1)

Thanks 2

4 Entries

12/5/2014 11:16 AM	Rate (0)
Tech74 Posts: 6 Rating: (0)	Hey there, First post here. I'm fairly new to PLC programming and need advice. I've searched the forum but could'nt exactly find my answers, so I'm asking here. I need to create the history of a task and save it into a DB, I've created arrays to fill. I figured I'm going to use SFC1 READ_CLK. The trick is: what language should I use, STL or SCL? I'm using a 300 series CPU. The problems are: 1) Transferring the DT. A DT variable weighs 64 bits and if I'm good I can't use the MOVE or LD (load) functions because the accumulator has a limit of 32 bits. Then should I split the DT variable and use two double words instead? 2) Shifting in the array. I'm no good at all with this kind of programming. How can I shift to a new line? Using an index? For (i=0, i<(size of array), i++)? If my array starts at DB2.DBX2.0 then I have to increment of 8 to DB2.DBX10.0, using a string of CHAR and INT? Another question that comes to mind is how to make sure I write on a new line, if the PLC reboots. In fact it's a PLC/NCK, so it will be rebooted on occasions. Can I read the lines of the DB and make sure I write on a line whose value is DT#90-1-1-1-0:0:0.000 (initial value)? Thanks for any help! Just to know what language I should use would be great!
Tech74 Posts: 6 Rating: (0)	Last edited by: Tech74 at: 12/5/2014 2:15 PM
Suggestion To thank Quote Answer

12/5/2014 11:38 AM	Rate (1)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 1/30/2025 Posts: 6859 Rating: (1366)	Tech74 Hey there, First post here. I'm fairly new to PLC programming and need advice. I've searched the forum but could'nt exactly find my answers, so I'm asking here. I need to create the history of a task and save it into a DB, I've created arrays to fill. I figured I'm going to use SFC1 READ_CLK. The trick is: what language should I use, STL or SCL? I'm using a 300 series CPU. The problems are: 1) Transferring the DT. A DT variable weighs 64 bits and if I'm good I can't use the MOVE or LD (load) functions because the accumulator has a limit of 32 bits. Then should I split the DT variable and use two double words instead? 2) Shifting in the array. I'm no good at all with this kind of programming. How can I shift to a new line? Using an index? For (i=0, i<(size of aray), i++)? If my array starts at DB2.DBX2.0 then I have to increment of 8 to DB2.DBX10.0, using a string of CHAR and INT? Another question that comes to mind is how to make sure I write on a new line, if the PLC reboots. In fact it's a PLC/CNK, so it will be rebooted on occasions. Can I read the lines of the DB and make sure I write on a line whose value is DT#90-1-1-1-0:0:0.000 (initial value)? Thanks for any help! Just to know what language I should use would be great! Hello Tech74, My own preferred language for such a task would be STL because it is easier and more tangible.For more information regarding STL,Please read more: Automating with STEP 7 in STL and SCL SIMATIC STEP 7 V5.5 Statement List (STL) for S7-300 and S7-400 Programming For other questions: Handling date and time variable with indirect addressing (How can you read out the date and time with SFC1 (READ_CLK) and input them with SFC0 (SET_CLK)? ) and all topics related to indirect addressing in STEP 7( STEP 7 -- Creating S7 programs -- Indirect Addressing).Access each byte from 8 bytes structure and copy it to the target structure with loop and indirect addressing. Using indirect addressing and Incrementing address registers facilitate the strategy you are looking for dynamically copying any amount of data from source to destination. Initialization strategies can be done via re-start OBs like OB100.In that block , you can initialize all emements of your DB with loop and indirect addressing. I hope these comments help you, Hamid Hosseini
	Last edited by: hdhosseini at: 12/5/2014 2:00 PM Demo Channel on Youtube
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users Tech74

12/5/2014 1:37 PM	Rate (0)
Tech74 Posts: 6 Rating: (0)	Thanks a lot! I'll use the tips.
Tech74 Posts: 6 Rating: (0)
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users hdhosseini

12/12/2014 2:36 PM	Rate (0)
Tech74 Posts: 6 Rating: (0)	Hey there, I'm back again. As I kept having syntax errors in LIST when programming very basic instructions (open a DB, load a DW and then transfer it to another DW) I've decided to use SCL instead. I programmed a function to be called. It's supposed to get the date, write it in a specific line of the DB that I use as a temporary storage line, and then transfer it to an array that is indexed on a counter (I need the number of events of a cycle and its history). Reading the array to find an "empty" line (with the initial DT value) proved too difficult at my level of skills. It goes like this: [code] FUNCTION FCXX : VOID TITLE = 'HISTORY' AUTHOR: Tech74 FAMILY: NAME: HISTO VERSION: '01.00' VAR_INPUT NUM_BYTE_DB: INT; // Specifies where the array starts END_VAR VAR_TEMP rv_sfc: INT; // Return_value of SFC1 "READ_CLK" index: INT; TAB : ARRAY[1..500] OF INT; // Array of 500 DT in the DB TAB2 : ARRAY[0..4000] OF INT; // 500*8 bytes BYTE_NUMBER : INT; // Where to write END_VAR BEGIN rv_sfc:=READ_CLK(CDT:=DB242.DATE_TEMP); // DB242.DBX4.0 BYTE 8 index := DB242.Nb_Cycles_Manu; // index = number of cycles done FOR index := 1 TO 499 BY 1 DO TAB[index]:=index; END_FOR ; FOR BYTE_NUMBER := (0+NUM_BYTE_DB) TO (3992+NUM_BYTE_DB) BY 8 DO TAB2[BYTE_NUMBER] := TAB[index]; END_FOR ; DB242.DBD[BYTE_NUMBER] := DB242.DBD4 ; // Transfer DT first 4 bytes from the temporary storage to the array DB242.DBD[BYTE_NUMBER+4] := DB242.DBD8 ; // DT last 4 bytes END_FUNCTION [/code] And of course, having the two arrays working together isn't successful, the date won't transfer. Any clue?
Tech74 Posts: 6 Rating: (0)
Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Follow us on