Equipments (Devices) > PLC200 > Program > String > STR

Block that performs the comparison between STRINGs.

Ladder Representation

STR_COMPARE_block

Block Structure

Variable Type	Name	Data Type	Description
VAR_INPUT	EN	BOOL	Block enabling
	STR1	STRING	First STRING of the comparison
	STR2	STRING	Second STRING of the comparison
	SENSITIVE	BOOL	Selects whether the comparison will be case insensitive or not
VAR_OUTPUT	DONE	BOOL	Output enabling
VAR_OUTPUT	COMP	BYTE	Value of comparison

Operation

This block remains active as long as EN is at TRUE level by updating the value of COMP according to the input STRINGs. The SENSITIVE input with value TRUE forces the comparison to consider uppercase and lowercase letters, while a FALSE value ignores this differentiation. The values that COMP can take are:

•	0, if both are the same;

•	-1, if STR1 comes first in alphabetical order;

•	1, if STR1 comes after in alphabetical order.

The comparison takes into account the values of the ASCII table for the characters.

The DONE value forwards to the next Ladder block the EN value when the operation is completed.

Compatibility

Device	Version
PLC300	2.10 or higher

Block Flowchart

STR_COMPARE_flowchart

Example in Ladder

STR_COMPARE_example01

In the above example, the ASCII code for 'a', first character of STR1, is smaller than that of 'c', first character of STR2. Thus, COMP receives the value -1. When the block is finished successfully, the DONE output is activated.

STR_COMPARE_example02

In the above example, the ASCII code for 'a', first character of STR1, is greater than that of '.', first character of STR2. Thus, COMP receives the value 1. When the block is ended successfully, the DONE output is activated.

STR_COMPARE_example03

In the example above, STR1 and STR2 are the same. Therefore, COMP receives the value of 0. When the block ends successfully, Done output is activated.

STR_COMPARE_example04

In the example above, STR1 and STR2 are the same, disregarding uppercase and lowercase (SENSITIVE with FALSE value). Therefore, COMP receives the value of 0. When the block ends successfully, Done output is activated.

STR_COMPARE_example05

In the example above, STR1 and STR2 are the different, considering uppercase and lowercase (SENSITIVE with FALSE value). The ASCII code for 'a', first character of STR1, is greater than that of 'A', first character of STR2. Thus, COMP receives the value 1. When the block is ended successfully, the DONE output is activated.

Example in ST

The example below displays the instructions for applying the example above in the ST language.

VAR

STR1 : STRING := 'abc';

STR2 : STRING := 'AbC';

SENSITIVE : BOOL := 0;

COMP : SINT;

END_VAR

COMP := FB_STR_COMPARE(

EN:=DI1,

STR1:=STR1,

STR2:=STR2,

SENSITIVE:=SENSITIVE,

Done=>DO1);