min/max value from DB

Siemens- STL?

Hi William,

Thanks for the response.

i think i understand how loop works. Please help me in defining a area of DB in a loop.

...

Thanks for the acknowledgement.
Have you read what Sydney has written?

I am going to leave you in the capable hands of the STL experts.
w

Sydney

Hello Siemens- STL?,

 Additionally if the searching doesn't start from the beginning of the DB you have to init the address register with the start value - change the instruction LAR1 P#0.0. You need the start address (if you have the index, multiply it by four), then shift to the left by 3 as doubleword (SLD 3) and save to address register (LAR1).

 The above Part is what i need Sydney. Thanks a lot.   its working now.  

i was wrong. i understood loop better only after you explaining it.

Thanks for explaining all the possibility. i will refer to this suggestion when required in later stages.

as im new to STL and as im basically a Rockwell person and with limited time in the task im doing. your suggestions are very helpful.

Looks like, as i didnt mention the data type of the variables used in the program in my previous Post. I think there was a little confusion. Actually i have the right data types used for address, index and variables.

i get the working area of DB from SCADA. so i calculate loop length and starting address and ending address based on that.

      L     #End_No_val

      SLD   3

      T     #Max_adrr

      L     #Min_No_Val

      SLD   3

      T     #Min_adrr

 OPN   DB300

      L     #Min_adrr

      LAR1  

//***** Init vars with the first value *****

      L     DBD [AR1,P#0.0]

      T     #rMin

      T     #rMax

      L     #Loop_Len

loop: T     #i

      +AR1  P#4.0

//***** Max value *****

      L     #rMax

      L     DBD [AR1,P#0.0]

      >R    

      JC    Max

      T     #rMax

      TAR1  #dwPtrMax

Max:  NOP   0

//***** Min value *****

      L     #rMin

      L     DBD [AR1,P#0.0]

      <R    

      JC    Min

      T     #rMin

      TAR1  #dwPtrMin

Min:  NOP   0

//***** Loop if not finish *****

      L     #i

      LOOP  loop

//********** Write output **********

      L     #rMin

      T     #Min

      L     #rMax

      T     #Max

      L     #dwPtrMin

      SRD   3

      T     #MinAddr

      L     #dwPtrMax

      SRD   3

      T     #MaxAddr

      L     #Max

      T     DB304.DBD12        // Output

      LAR1  #dwAR1save

      SET   

      SAVE  

//********** Block end **********

      BE 

Sydney

Hello Siemens- STL?,

don't know why you calculate the position with the real numbers (floating point), but anyway - you changed the wrong part of the code. I don't know if I get it right - you would like to finish at position #Min_No_Val, or you want to go from this position to another calculated position? Now the procedure goes from the beginning of the DB and finishes after the number of loops defined in #i. If you want to go from calculated position to the another position, you have to also change the start offset in address register.

Let me first clarify the meaning of the variables. The loop procedure could stay as it is in the origin code. At the beginning the index #I should contain the number of compared DB members, which is the number of loops here. It is decremented by one each loop and finishes at zero. On the other hand the address register should always contain the actual address of the compared member, which is in this case four times more then position index. You should decide from which data you get the members - is it their position index or their address in the DB (index * 4)? And the important thing - the calculation with indexes or addresses is typed as integer numbers.

Now you should change only the initial part of the code. As first you have to init the #i with the number of loops. If it starts from the beginning of the DB then the #i is equal to the last index (starts from zero) or the last address divided by four. If you search some part in the DB the #i is obtained by a subtraction of the indexes or in the case of addresses the result have to be divided by four. Additionally if the searching doesn't start from the beginning of the DB you have to init the address register with the start value - change the instruction LAR1 P#0.0. You need the start address (if you have the index, multiply it by four), then shift to the left by 3 as doubleword (SLD 3) and save to address register (LAR1).

 Hi Sydney...

What if i start at a DBD address (Say DBD40) and go searching, Decrementing down towards starting of the DB (say DBD 8). though condition gets satisfied at many position in defined DB area. i need to see the output having address of lower most DBD position.

achieved the opposite. But not sure how to search down the DB. Defining the start address as a higher DBD position.

Pls suggest.

Hello,

the solution is pretty easy - if you want to go through the data in opposite direction, you have to init the address register with the last address and then decrement it by four bytes in each loop. The instructions in your case are:

      L     #Max_adrr

      LAR1  

      ...

loop: T     #i

      L    -32    // -4 Bytes

      +AR1

      ...

Regards

Sydney

Hi

Function attached (as a printout and a AWL source).

It finds the min and max of selected data type (byte, int, word, dint, dword, real) in selected

data block.

You must specify

- data block

- starting address (address of first element)

- number of elements (for example when REAL selected put 10 to test 10 consecutive real numbers)

- data type

function returns

- min and max on output for selected data type

- zero on all other outputs

- ENO=1 when OK or ENO=0 when fault (wrong arguments).

When ENO=0 all outputs are 0

NOTE:

Byte is unsigned (0..255)

Int / DInt are signed integers (int: -32768 .. 32767; dint: -2147483648 .. 2147483647)

Word / DWord are interpreted as Unsigned Integers (word: 0..65535, dword: 0..4294967296)

Regards

Piotr

Sydney

Hello,

the solution is pretty easy - if you want to go through the data in opposite direction, you have to init the address register with the last address and then decrement it by four bytes in each loop. The instructions in your case are:

      L     #Max_adrr

      LAR1  

      ...

loop: T     #i

      L    -32    // -4 Bytes

      +AR1

      ...

Regards

Sydney

 Hi Sydney,

i have a situation here. Pls help.

Im getting a Junk value like 12306. if the Max value is at the  "#Min_adrr" that i specify!. 

it is the same value that im getting, if the max value is at the Starting point (in the DB)that i specify

*************************

 OPN   DB300

      L     #Min_adrr

      LAR1  

*************************

Pls refer to the same program that is 2 posts above, pls.

waiting for your valuable suggestions.

Hello,

sorry I didn't understand what is the problem now, where you get the wrong number? Have you tried the suggestion from my last post? You should init the address register with the max address at the beginning and at the end of loop decrement it.

Regards

Sydney

Hi Sydney,

this program doesnt have the decrementing way of checking. it is like the one before, that we discussed.

For example im looking for the max value in DB from DBD 4 to DBD 100...

If the highest value is at DBD 4(that is, #Min_adrr ) im getting the output address(MaxAddr) as a junk value like 123056. otherwise, if the Max value is at any other location in the defined area of DB. im getting the correct DBD number as the output in #MaxAddr.

in other words, if the highest value in the the DB is present at the #Min_adrr i give. im getting an inappropriate value like 123506, if the max value is at any other location after Min_adrr, then output is perfect.

Please suggest.

TAR1  #dwAR1save

  OPN   DB [#DB_Temp]

      L     #Min_adrr

      LAR1  

//***** Init vars with the first value *****

      L     DBD [AR1,P#0.0]

      T     #rMin

      T     #rMax

      L     #Loop_Leng

loop: T     #i

      +AR1  P#4.0

//***** Max value *****

      L     #rMax

      L     DBD [AR1,P#0.0]

      >R    

      JC    Max

      T     #rMax

      TAR1  #dwPtrMax

Max:  NOP   0

//***** Min value *****

      L     #rMin

      L     DBD [AR1,P#0.0]

      <R    

      JC    Min

      T     #rMin

      TAR1  #dwPtrMin

Min:  NOP   0

//***** Loop if not finish *****

      L     #i

      LOOP  loop

//********** Write output **********

      L     #dwPtrMax

      SRD   3

      T     #MaxAddr

Now it's clear to me, sorry when the address output was added it was done only after satisfied comparison, but it has to be also filled first in the init part:

//***** Init vars with the first value *****

      L     DBD [AR1,P#0.0]

      T     #rMin

      T     #rMax

      TAR1  #dwPtrMin

      TAR1  #dwPtrMax

Regards

Sydney

New question published by Siemens- STL? is split to a separate thread with the subject After save, converted into STL and doesnt go back to FBD.

Best regards
Min_Moderator