Hi all.

After finding so much knowledge here over the years, I'm now at a complete loss and hope someone can help me out as well!

This is a long post as I have tried to include all pertinent information... (and I am a wordy person )

I have a FB written in SCL which loops through an array of structs. Each element in the struct holds information such as if a data source is remote/local, active/inactive and the communication ID# in case it is a remote source. It will also specify a bit-offset from dbx0.0 in the source DB, as some sources can have one, two or three bytes in their DB (individual, not array of bytes).

Definition and assignment of the one I'm working with:

STRUCT
  sources: ARRAY[0..15] OF STRUCT
    src_name:     STRING[32] := 'Spare';
    active:       BOOL  := false;
    remote:       BOOL  := false; // Local station if false, remote station if true
    read_error:   BOOL  := false;
    alarm_flags:  BYTE  := 16#0;  // The error flag from SFB14-SFC20
    status_word:  WORD  := 16#0;  // The status word from SFB14-SFC20
    com_id:       WORD  := 16#0;
    bit_offset:   WORD  := 16#0;  // number of bits offset from the start of DB400 of the remote station
    alarm_count:  INT   := 0;
  END_STRUCT;
END_STRUCT

BEGIN

sources[1].src_name     := 'Keg 1';
sources[1].com_id       := 16#21;
sources[1].remote       := true;
sources[1].bit_offset   := 16#0;
sources[1].active       := true;

 I have used the information In this post (and others) to work with any-pointers so that I can make up the source pointer for each active source on the fly.

The source DB is always DB400, and the data starts at address 0 in the DB.

The destination DB is always DB402 in the local PLC and it holds one byte. (I will only ever read one byte at a time, even from the sources with more bytes in their DB400)

I tried it first with local data. The source and destination pointers are made up the same for local and remote data. If the data is local I use the source and destination ANY-pointers in SFC20 (BLKMOV), and this worked perfectly. The bit-offsets also worked.

_retval := SFC20(SRCBLK := _p_any_source, DSTBLK := _p_any_dest);

 Now I am starting to try with the remote data, using SFB14 (GET), and this is where the fun ended.

This is how I make up the ANY-pointers:

_source_any_ptr.s7_code          := 16#10;// constant
_source_any_ptr.data_type        := 16#02;// Byte access (always in this application)
_source_any_ptr.length           := 1;    // 1 byte in length
_source_any_ptr.db_number        := 400;  // Remote DB number. All are 400
_source_any_ptr.memory_area      := 16#84;// Shared DB memory area
//_source_any_ptr.byte_address_LSB := Remote_Alarm_DB.sources[array_pointer].bit_offset;
_source_any_ptr.byte_address_LSB := 16#0; // For testing... made no difference
_source_any_ptr.byte_address_MSB := 16#0; // Always 0 for this application

_dest_any_ptr.s7_code          := 16#10;  // constant
_dest_any_ptr.data_type        := 16#02;  // Byte access (always in this application)
_dest_any_ptr.length           := 1;      // 1 byte in length
_dest_any_ptr.db_number        := 402;    // Local DB number, always 402
_dest_any_ptr.memory_area      := 16#84;  // Shared DB memory area
_dest_any_ptr.byte_address_LSB := 16#0;   // gives the bit address in the DB for the current array byte
_dest_any_ptr.byte_address_MSB := 16#0;   // Always 0 for this application

 If I call it in my FB using an instance, defined as such:

Get_Alarm_Data:     SFB14;

 and the call looks like this:

Get_Alarm_Data(REQ := get_remote_data,
     ID := 16#21,
     ADDR_1 := _p_any_source,
     RD_1 := _p_any_dest);

( The routine is called every scan, and the REQ-variable controls if it is active or not. Here, for testing, I entered the ID explicitly, rather than using the data in my control array. It made no difference.)

 The issue? I get no data, but instead I get an error flag and status 4, something wrong with the DB address or data types not matching.

Next I try to add an instance of SFB14 to the project, called it FB15 and added an instance DB, DB15, and called that from my SCL source, like so:

fb15.db15(REQ := get_remote_data,
     ID := 16#21,
     ADDR_1 := _p_any_source,
     RD_1 := _p_any_dest);

 With this I still get an error flag, but instead I get status 1.

Third try... I disable these calls and instead add FB15 to OB1 and populate it with the following parameters:

ID: W#16#21

ADDR_1: DB400.DBX0.0 BYTE 1

RD_1: DB402.DBX0.0 BYTE 1

 And this works perfectly!

There is clearly something here that I am missing, but I can't for the life of me figure out what... Three ways of calling with three different results, and SFC20 does not complain with the same address parameters...

Any help would be greatly appreciated!

Cheers, Mattias

[Attached ]is the whole SCL code, it might help to paste in an editor to get highlighting

Hi 0_Einstein

The PLC is an S7-300 (IM151-8), and SFB14 is the GET FB. I'm using the latest version of Step 7 (5.7+sp3).

Cheers, Mattias

For anyone else ending up here...

I was not able to get this to work as I wanted. I can make any-pointers which work with BLKMOV (SFC20), but the same pointers do not work with SFB14(GET). Every on-line instruction says it should work, so I am clearly doing something wrong.

In my code, I am always reading from DB400, and the variable is which byte I read from. 0, 1 or 2. So in the end I solved it by having 3 GET-blocks, and each is pre-programmed with "DB400.DBX0.0 BYTE 1" or "DB400.DBX1.0 BYTE 1" or "DB400DBX2.0 BYTE 1". No ANY-pointer in sight. I then toggle the EN-pin on the one I need to use, with the others being off. I also change which communications ID is used for each call to target the correct PLC.

Not a "pretty" solution, but the only one I could get to work, and in the end I can't spend weeks on this problem just to make it pretty :-)

Should you figure it out, then please add a solution here. I will change my code in a heartbeat!

// Mattias