Automation– and Drive Technology- SCE
There are three possibilities to access the data:
1. Direct address access:
One can access one data element in a data block with the following instructions:
Example: |
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L | DB 20. DBB2 | Load data byte 2 from DB20 into ACCU 1 |
L | DB 22. DBW4 | Load data word 4 from DB22 into ACCU 1 |
A | DB 2. DBX5.6 | Carry out an AND- logical operation with data bit 5.6 from DB2. |
2. Access to the data elements in the already opened data blocks:
In order to be able to access a data element over several data elements, the DB must first be opened with the instructions OPN DB or OPN DI. Then several data bits (DBX/DIX),data bytes (DBB/DIB), data words (DBW/DIW) or data double words (DBD/DID) can be processed in digital or binary operations.
In doing so, one especially uses OPN DI for the opening of instance DBs. It can also be used for global DBs, when 2 DBs remain open at the same time.
Example: |
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OPN | DB 20 | Opening of DB20 |
OPN | DI 22 | Opening of DB22 |
L | DBW 0 | Download data word 0 from DB20 into AKKU 1 |
T | MW 1 | Transfer the contents from ACCU 1 to memory bit 1 |
A | DIX 0.0 | AND- Operation from data bit 0.0 to DB22 with |
A | I 1.0 | input bit 1.0 |
= | Q 4.0 | Assignment of the result to output bit 4.0 |
3. Access to data out of local instance DBs by call with the function block:
Data can be transferred by the call of the corresponding instance data block with the instruction CALL FB1, DB19. The assignment of the variables that would be defined in the declarations table of the FB and whose value stands in the DB, take place directly in the absolute address (e.g. IW0, M 10.0 or QW4) with the CALL instruction.
Example: |
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CALL | FB1, DB19 |
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COUNT:= | IW 0 | The variable COUNT is assigned to IW 0 as an absolute address. |
OUT:= | Q 4.0 | The variable OUT is assigned to Q4.0 as an absolute address. |
Note: | The format of the variables and the assigned absolute address must be equal. | |
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Forward | Notes | Generating data blocks |
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T I A Training document | Page 17 of 18 |
| Module B4 | |
Last revision: 02/2002 |
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| Data blocks | |